Retiring from competitive competitive programming, ideal form of a competitive programming website. I tried to create a community
where the legends, /motivation to keep the top form and be prepared to win the next contest. I
think I've done, I started my career as a competitive math-puzzle solver in 1999. The first
contest was a local one
→ Pay attention
→ Top rated
| # | User | Rating |
|---|---|---|
| 1 | Benq | 3857 |
| 2 | jiangly | 3810 |
| 3 | maroonrk | 3534 |
| 4 | tourist | 3528 |
| 5 | Kevin114514 | 3510 |
| 6 | turmax | 3411 |
| 7 | Um_nik | 3387 |
| 8 | Radewoosh | 3367 |
| 9 | heuristica | 3322 |
| 10 | strapple | 3317 |
→ Top contributors
| # | User | Contrib. |
|---|---|---|
| 1 | Qingyu | 158 |
| 2 | maspy | 150 |
| 3 | Um_nik | 146 |
| 4 | Errichto | 139 |
| 5 | adamant | 136 |
| 6 | maroonrk | 134 |
| 7 | DNR | 133 |
| 8 | nik_exists | 131 |
| 8 | Dominater069 | 131 |
| 10 | Proof_by_QED | 130 |
→ Find user
→ Recent actions
You can use several words in query to find by all of them at the same time. In addition, if you are lucky search understands word forms and some synonyms. It supports search by title and author. Examples:
305— search for 305, most probably it will find blogs about the Round 305andrew stankevich contests— search for words "andrew", "stankevich" and "contests" at the same timeuser:mikemirzayanov title:testlib— search containing "testlib" in title by MikeMirzayanov"vk cup"— use quotes to find phrase as istitle:educational— search in title
Results
1.
Retiring from competitive competitive programming Recently, I feel I've passed my peak as a competitive programmer, and ran out of sufficient energy/motivation to keep the top form and be prepared to win the next contest.
I think I've done everything I can do as a competitive programmer, and now it's time to end my career as a professional (mind) sport player.
It was a great experience.
I'd like to thank everyone involved in the community, especially:
- Competitors. It was always nice to compete against you all!
- Problem writers who gave great problems to the community.
I started my career as a competitive math-puzzle solver in 1999.
The first contest was a local one named "junior sansu (arithmetic) olympiad".
Since then, I enjoyed this sport a lot for 21 years.
In 2007, I started TopCoder, and it changed my life.
The problems were great, and every single match of SRM felt like a once-in-a-life event.
A lot of legends were competing there — [user:Petr,2020-12-31], [user:tomek,2020-12-31], [user:ACRush,2020-12...
2.
Codeforces Round #733 (Div. 1 + Div. 2) Hello, Codeforces!
Welcome to the [contest:1530] that will start on [contest_time:1530]. It will be a combined rated round for both divisions.
This round is a mirror of VK Cup 2021 Elimination. VK Cup is an annual championship for Russian-speaking competitors organized by VK — a social networking service based in Saint Petersburg and the most popular website in Russia. VK Cup [started in 2012](https://codeforces.me/vkcup2012) and has grown to be a four-track competition in competitive programming, ML, design, and mobile development.
All the problems were authored and prepared by me. Big thanks to everyone without whom this round would not be possible: [user:PavelKunyavskiy,2021-07-16], [user:KAN,2021-07-16], [user:lperovskaya,2021-07-16], [user:ksun48,2021-07-16], [user:Sert,2021-07-16], [user:Aleks5d,2021-07-16], [user:MikeMirzayanov,2021-07-16].
You will be given 8 problems and 3 hours to solve them. It is recommended to read all the problems. Good luck!
**UPD*...
Hello, Codeforces! Welcome to the [contest:1530] that will start on
[contest_time:1530]. It will
Announcement of VK Cup 2021 - Elimination (Engine)
3.
Rule Restricting the Use of AI [revision 2024-09-14] It seems that neural networks are working technological wonders. Not long ago, they struggled with even the simplest tasks in our competitions, but now they are reaching new heights that cannot be overlooked.
There is reason to believe that progress will continue, and we can expect further advancements in neural networks within the realm of programming competitions.
For this reason, we are explicitly limiting the use of AI-based systems (such as various models like GPT, Gemini, Gemma, Llama, Claude, and others) for solving programming problems.
However, we recognize that AI can be a valuable tool for learning and coding assistance, so we aim to establish clear boundaries for its use.
**Application of this Rule:**<br/>This rule applies strictly to in-contest participation. This includes both registered contestants and out-of-competition participants in any rated Codeforces round. If a round is unrated and this is explicitly stated in the round announcement or rules, the rul...
advancements in neural networks within the realm of programming competitions.
For this reason, we are
4.
Codeforces Round #639 Hello, Codeforces!
I'm very glad to invite you to [contest:1344] and [contest:1345]. This contest will take place on [contest_time:1344]. In both divisions, you will have **2 hours 15 minutes** to solve **6 problems**. The score distribution will be announced closer to the start of the contest.
Of course, this round would not be possible without the help of many people, who I'd like to thank:
- [user:isaf27,2020-05-01], for coordinating this round, and helping with solution ideas.
- My ICPC teammates [user:Kuroni,2020-05-01] and [user:strongoier,2020-05-01], and coach [user:cn355,2020-05-01], for encouraging me to pursue competitive programming. In particular, I'd like to thank [user:Kuroni,2020-05-01] for being so spectacularly bad that a barely-orange user like myself actually has a place on our team.
- [user:300iq,2020-05-01], [user:antontrygubO_o,2020-05-01], [user:Ari,2020-05-01], [user:ffao,2020-05-01], [user:fpc_coder,2020-05-01], [user:gamegame,2020-05-01], [user:Kur...
Hello, Codeforces! I'm very glad to invite you to [contest:1344] and [contest
:1345]. This
Announcement of Codeforces Round 639 (Div. 1)
Announcement of Codeforces Round 639 (Div. 2)
5.
My opinion on how to practice competitive programming I'm not very often replying to questions about how to practice, but as I'm getting enough of them (and I've just seen another blog about practicing) let me tell you about it.
Of course, every time when you ask someone good about how to practice, he/she will reply to you to "solve a lot of problems" and that's true, there's no other way. Anyway, I've thought about it and actually I'm able to tell a bit more. I know some people, I've seen many people practicing (including me) and I have an opinion.
Many people practice in some organized way. High schools organize IOI/OI training contests every Saturday, universities organize ICPC training contests once a week, people try by their own to solve three problems each day, websites host rounds and so on. Here's a secret: it's a sh*t. Yep, that's true. If you want to be really good and to make it happen you compete in a training once a week, you do it only to be able to make excuses "but I'm training so hard" when you see no progress.
...
My opinion on how to practice competitive programming, for sure compete in this contest virtually or something, don't force yourself,
just really feel a, practice and become strong, you'll for sure compete in this contest virtually
or something, don't
6.
Codeforces celebrates its 15th anniversary! <img src="https://assets.codeforces.com/files/codeforces15.jpg" style="width:250px; float:right; margin: 0 1em 1em 1em;" />
Hi, Codeforces!
Around this time, 15 years ago, I was deploying the first version of Codeforces on a server, registering my account, and writing the first post. 15 years have passed. Well, happy anniversary to us!
For me, this is the most exciting adventure — full of ups and downs, hard work, and moments of joy. What's amazing is that it was never a lonely journey. I've always had caring and reliable friends by my side! That includes the Codeforces team, coordinators and problem writers, our partners in various events, all community members, and, of course, our sponsors — steadfast supporters and helpers.
Look at what we've accomplished together! Here are some of the key metrics over the years. There seems to be plenty to celebrate!
<center>
<img src="https://assets.codeforces.com/files/15/01-submissions.png" class="resource" style="width:300px;"/>...
" style="width:300px;"/>
7.
Codeforces EDU: β-testing (Now in English!) <img src="/predownloaded/47/86/4786c2ec901c0b5b490794ca6fd5145f0dcdeae3.png" style="float:right; width: 400px; margin: 0 1em 1em 1em"/>
Hello Codeforces!
In February, in the Russian-language interface, we announced a new educational subsection of the website. It's time to go international!
I am pleased to invite you to test the new section, which so far has the working title EDU. I hope that someday EDU will become a real educational hub for fans of programming competitions. It will be great to have in one place the collected educational content with text and video materials, with selected thematic problems.
At the moment, its functionality is still under development, and here is the current progress and <i>β</i>-testing preview. Write your comments and suggestions in the comments here.
<center style="margin:2.5em;">
<a href="/edu/courses" style="text-decoration:none; font-size:18px; background-color:#01579B; color:white; font-weight:bold; padding:0.5em 1em;">Go to EDU ...
that someday EDU will become a real educational hub for fans of programming
competitions. It will be
8.
0 Problems Remaining [日本語記事(For Japanese Speakers)](https://maspypy.com/codeforces-all-ac)
----
Previous post: https://codeforces.me/blog/entry/150057
Submission: [submission:384239819]
2026/07/26 03:13:42 JST (2026/07/25 18:13:42 UTC)
I have solved every problem in the Codeforces PROBLEMSET except for those for which I determined that obtaining an accepted verdict is impossible.
# Scope
I considered the problems listed in the [PROBLEMSET](https://codeforces.me/problemset).
I have solved very few problems from the [GYM](https://codeforces.me/gyms). The only collection I worked through systematically was the PROBLEMSET.
I determined that it is theoretically impossible to obtain an accepted verdict for the following 31 problems:
[problem:775A], ([92101](https://codeforces.me/problemset/problem/921/01) ... [92114](https://codeforces.me/problemset/problem/921/14)), [problem:927A], [prob...
goal, comparable to the satisfaction of placing highly in a contest or
watching one’s rating, contest would clearly be cheating. - As far as I could determine, I found no
rule prohibiting
9.
Codeforces: Results of 2023 [Annual Report] Hello, Codeforces.
Let's recall 2023, shall we?
In this post, I want to summarize this year. You know, a lot of terrible things happen in the world, and personally, this year was the hardest and most sorrowful for me. But today, we'll remember something else. We'll remember what this year was like for Codeforces.
Recently, Codeforces turned 14 years old. Not bad, right? And for many years now, when asked "What is Codeforces?" the first thing I say is — it's a community!
[cut]<br/>
#### Personal Thanks!
On behalf of the community (and myself), I say thank you to everyone who tries, helps, and makes efforts to keep the community alive.
Thank you to the developers! Although I continue to engage in development and other technical activities, I'm glad that these guys made an effort and improved the platform: [user:geranazavr555,2024-02-04], [user:unreal.eugene,2024-02-04], [user:vbandurin,2024-02-04], [user:ChurakovaAlexandra,2024-02-04], [user:medvezhonokok,2024-02-04]...
micro-websites against brute force attacks on the login page. * Several fixes
in thecontest proposal, contest problems on a single page * Functionality to run solutions with custom
inputs directly on the
10.
Linear Recurrence and Berlekamp-Massey Algorithm **#IjustWantContribution**
It seems there isn't any blog about Berlekamp-Massey Algorithm around here, so I decided to go on a try. :P
Acknowledgement: Hats off to matthew99 for introducing this algorithm.
#### What is 'linear recurrence'?
Assuming there is a (probably infinity) sequence $a_0,a_1...a_{n-1}$, we call this sequence satisfies a linear recurrence relation $p_1,p_2...p_m$, iff $\forall i \geq m,~a_i=\sum_{j=1}^m a_{i-j}p_j$. (Obviously, if $m\geq n$ any $p$ can do :P)
#### How to calculate k-th term of a linear recurrence?
For a polynomial $f(x)=\sum_{i=0}^{t} c_ix^i$, we define $G(f)=\sum_{i=0}^{t} c_ia_i$.
Obviously $G$ satisfies $G(f)\pm G(g) =G(f \pm g)$.
Because $a_i=\sum_{j=1}^m a_{i-j}p_j$, if we let $f(x)=x^m-\sum_{j=1}^m x^{m-j}p_j$, then $G(f)=0$. Also $G(fx),G(fx^2)...=0$. So $G(fg)=0$ (g is any polynomial).
What we want is $G(x^k)$. Because $G(f\lfloor x^k/f\rfloor)=0$, then $G(x^k)=G(x^k \bmod f)$.
[cut]
We can calculate $x^k \b...
. #### Try your hands http://codeforces.me/contest/506/problem/E Write a naive
dynamic-programming, http://codeforces.me/contest/506/problem/E Write a naive dynamic-programming
for small n, plug in
11.
The 2025 Universal Cup Finals The best and brightest programmers from around the world have gathered this week in Dongguan, China, for the highly anticipated 2025 Universal Cup Finals!
<center>
<img src="/predownloaded/b8/c4/b8c48453572a7a497d0be10c665c67bfe5074593.jpg">
</center>
### Event Details
- Date: Saturday, February 22nd
- Start time: 10:30 AM CST (2:30 AM UTC)
- See [participating teams](https://codeforces.me/blog/entry/136593)
- Full schedule can be found [here](https://ucup.ac/news/announcement-2025-ucup-finals/)
### Streaming
Witness the best contestants in the world as they push the boundaries of skill and strategy. You can be part of this event by following us online either on [English Channel](https://www.youtube.com/@que_tourist) or [Chinese Channel](https://live.bilibili.com/11464806).
### Mirror Contest
Join the mirror contest and compete in real-time with the finalists from anywhere in the world. Any Universal Cup registered team can participate. The mirror contest is ...
/11464806). ### Mirror Contest Join the mirror contest and compete in real-time
with the finalists
12.
Competitive Programming Hall of Fame — cphof.org Hi Codeforces!
Today I'd like to introduce the new [Competitive Programming Hall of Fame](https://cphof.org) project that is available at [cphof.org](https://cphof.org)
#### Background
A long time ago I've noticed that there is no single source of information with the results of previously held large programming competitions. Moreover, plenty of older championships don't maintain their websites anymore, and it becomes hard or even impossible to find any details about them, which is pretty sad. So I've decided to create [Competitive Programming Hall of Fame](https://cphof.org).
#### About the project
Competitive Programming Hall Of Fame is a project created to preserve the history of international championships in competitive programming. This website collects the results of the final stages for both worldwide and regional contests. By international championship we mean a contest consisting ...
Competitive Programming Hall of Fame — cphof.org, Bayan Programming Contest and CodeChef SnackDown, also fall into this
category. - **Local Contests, creating resources that share our mission to preserve the history of
competitiveprogramming contests, different limits on the number of local and international finalists, like Bayan
Programming Contest, для локальных и международных участников (например, Bayan Programming Contest,
CodeChef SnackDown, Competitive Programming Hall Of Fame is a project created to preserve the
history of international, Programming Contest, CodeChef SnackDown). - **Local Contests** — чемпионаты, не
подошедшие под
13.
Codeforces Round #633 **내가 돌아왔다!** (Hello, Codeforces!)
I am thrilled to introduce you to [Codeforces Round #633](https://codeforces.me/contests/1338,1339). Followings are basic information:
- This contest will take place on [contest_time:1338].
- The round is **rated for all participants** who can understand this announcement. There will be two divisions.
- There are **5 problems** in each division and you will have **2 hours** to solve it.
- Score distribution will be announced later.
Followings are contributors:
- **Authors**: [user:McDic,2020-04-10] (All Div.2 problems and Div.1 D), [user:tzuyu_chou,2020-04-10] (Div.1 E)
- **Coordinator**: [user:antontrygubO_o,2020-04-10]
- **Testers**:
- **Phase 1** (When this round was supposed to be Div.2): [user:dorijanlendvaj,2020-04-10], [user:SoulTch,2020-04-10], [user:pajenegod,2020-04-10], [user:AryaPawn,2020-04-10], [user:Rahul,2020-04-10], [user:mcdx9524,2020-04-10], [user:300iq,2020-04-10], [user:Nemo,2020-04-10], [user:tfg,2020-04-10]...
said in my last round's announcement. Polygon is super great platform to
prepare sportsprogramming, programming contest. Followings are some fun things: -
[user:antontrygubO_o,2020-04-10] is the
Announcement of Codeforces Round 633 (Div. 1)
Announcement of Codeforces Round 633 (Div. 2)
14.
How to practice Competitive Programming [Um_nik version] CP is about solving problems fast. And as absurd as it may sound, I believe that <span style="color:blue">SOLVE</span> and <span style="color:red">FAST</span> are very different and almost independent parts, and you need to practice them separately.
Let’s look at some <span style="color:red">contest</span>, like a CodeForces round. For the sake of simplicity let’s assume that every problem has some *difficulty*, which is a numerical value denoting how hard it is, bigger values correspond to harder problems (it is not true, but it is an ok-ish approximation, at least if we consider subjective difficulty for a fixed person). Contests are made for a wide range of participants, and problemsetters strive to make contests interesting for a wide range of participants, which means having a *smooth difficulty gradient*. Well... as smooth as it is possible with 5-6 problems.
<spoiler summary="Graph 1">
![ ](https://s3.us-west-2.amazonaws.com/secure.notion-static.com/677e0ae2-a8df-4874-aff...
How to practice Competitive Programming [Um_nik version], difficulties and doesn’t have a time limit. It is not a contest, it is an, when there is a contest that fits into your schedule, you shouldn’t miss it.
Turn to archive when, ">contest, like a CodeForces round. For the sake of simplicity let’s assume
that every problem has, ="color:red">contests, contest problems need to be fresh. - Where will we learn
stuff if in, Let’s look at some contest, like a CodeForces round. For the sake of, On the moment of a contest you have some ability to solve problems, Since one contest has only a few problems and should cover a wide, What I’m trying to convey is that in a contest your goal is to solve
15.
I compiled a list of almost all useful blogs ever published on Codeforces [update: till 09.06.2021] <h3 style="color:red">If there are any blogs that I have missed, please tell in the comment section. Thank you.</h3>
# Mathematics Stuff
- [Number Theory in Competitive Programming [Tutorial]](https://codeforces.me/blog/entry/46620)
- [Number of points on Convex hull with lattice points](https://codeforces.me/blog/entry/62183)
- [FFT, big modulos, precision errors.](https://codeforces.me/blog/entry/48465)
- [Number of ways between two vertices](https://codeforces.me/blog/entry/19078)
- [Mathematics For Competitive Programming](https://codeforces.me/blog/entry/76938)
- [FFT and NTT](https://codeforces.me/blog/entry/19862)
- [Burnside Lemma](https://codeforces.me/blog/entry/51272)
- [Number of positive integral solutions of equation 1/x+1/y=1/n!](https://codeforces.me/blog/entry/76836)
- [On burnside (again)](https://codeforces.me/blog/entry/64860)
- [Simple but often unknown theorems/lemmas/formula? Do you know?](https://codeforces.me/blog/entry/55912)
- [Probabili...
# Dynamic Programming - [Everything About Dynamic Programming
](https://codeforces.me/blog/entry, . Thank you. # Mathematics Stuff - [Number Theory in Competitive Programming
[Tutorial, ] — tools for competitive programming](https://codeforces.me/blog/entry/60627)
- [(almost) Every
16.
Red Isn't Impossible _I waited for more than a year to write this blog._
I started CP in July 2017, I always dreamed about reaching red, and it finally happened. I didn't become red like talented contestants in 1-2 years, but it took me more than that.
The start of my CP journey was average (you can see my graph); It took me more than six months to reach pupil, then another six months to get specialist, and it took me more time to achieve higher ranks. I didn't have any mentor or coach. So, I asked many stupid questions, which you can find if you read my old blogs. One of these questions is, "What's the importance of Dynamic Programming?" (I drafted this blog xD), But of course, I don't motivate people to ask these types of questions as they usually can be answered by just searching.
I failed many times during my journey in CP, especially in important competitions (IOI21 and IOI22). I stopped CP many times because I was frustrated and believed I could never improve. For example, I stopped when I w...
importance of Dynamic Programming?" (I drafted this blog xD), But of course, I
don't motivate people to
17.
Testing Round 20 [Communication Problems] Hello Codeforces.
We are introducing a new type of problem which may appear in future Codeforces rounds, called Communication problems!
In these problems, your program would be ran twice, with different input and output formats between the runs. All variables stored in the memory will be lost between runs. However, the information given to you on the first run may be important to you for completing the second run correctly. Therefore, one of the key challenges in these types of problems would be to find a way to use the limited amount of output you are given in the first run to communicate information to the second run. Below shows a flowchart.
<center>
<br/>
<img src="https://i.ibb.co/JWMFpyfY/a-1.png" alt="2025-09-06-12-40-07" border="0" />
<br/>
Flowchart for communication problems
</center>
In these problems, time and memory limits for both runs would be kept separately. For example, if a problem has a time limit of $2$ seconds, you will only get the Time Limit E...
rounds, called Communication problems! In these problems, your program would
be ran twice, with
Announcement of Testing Round 20 (Unrated, Communication Problems)
18.
[Tutorial] Generating Functions in Competitive Programming (Part 1) Hi everyone! Inspired by the recent [Codeforces Round 641](https://codeforces.me/contest/1349), I decided to write an introductory tutorial on generating functions here. I am by no means an expert in generating functions so I will write about what I currently know about them. [user:MiFaFaOvO,2020-05-15] has written a really interesting [blog](https://codeforces.me/blog/entry/76447) here on Codeforces about more advanced applications of generating functions, but I think there is no English tutorial on the basics of this topic yet (or at least on CP sites). Thus, I would like to share about this topic here.
I plan to split this tutorial into two parts. The first part (this post) will be an introduction to generating functions for those who have never learned about them at all, and some standard examples and showcases of generating functions. The second part will be a collection of several applications of generating functions in CP-style problems. If you are already familiar with ge...
[Tutorial] Generating Functions in Competitive Programming (Part 1), Hi everyone! Inspired by the recent [Codeforces Round
641](https://codeforces.me/contest/1349), I
19.
Codeforces: summing up 2016 year <center>
<img src="http://assets.codeforces.com/images/Happy-New-Year-HD-Wallpapers.jpg"/>
</center>
Somehow it turns out that for me, each coming the New Year means more and more. This is an excellent opportunity to take stock, to breathe fresh air and to go through a kind of catharsis. This is a rare opportunity to be with the family, dress up in Santa Claus and just have fun.
Holidays give me a clear criterion that I do the right things. If during the holidays, I begin to think about it, to recall some deferred ideas, eager to implement something new. So I’m doing right things. My things. And now exactly the same as in several recent years: during New Year holidays I write code for Codeforces, trying new technology or simply I’m making minor changes in testlib. It is necessary to me: at this moment are no deadlines, do not press the obligation. Just now, at 3 am, I can not break away from being able to do something new. I would like to take a moment and realize that spun in ...
We are always pleased when companies pay attention to the programming contest
whether in order to, programming contest whether in order to find the brightest talent (yes, you
are!) candidates
20.
AtCoder Library Recently, the number of algorithms and data structures we use in competitive programming are rapidly growing.
It's a nice thing: by using more algorithms, the variety of possible problems gets wider, and we can enjoy more problems.
On the other hand, before reaching adhoc, thinking-oriented part of this competition, we have to spend more and more time to learn algorithms.
Sometimes a problem asks matching on general graphs; you have to find a paper describing it, read it, and implement its really complicated algorithm. Or sometimes you have to spend time tuning your library by a constant factor. Or sometimes you use multiple pre-written codes together, the variable names collide, and get annoyed.
Until now, I basically rejected all problems that require pre-written codes of complicated algorithms because I don't like these things. For example, we never used segment trees with lazy propagation in our contests.
However this way we can't use otherwise interesting problems and it ...
Recently, the number of algorithms and data structures we use in competitive
programming are
21.
On Problems vs. Questions in Competitive Programming: My solution _TL;DR: The most reasonable solution to the problems vs. questions debate is to use none of the currently accepted terms._
As we have seen many times, particularly over the past few days, the task of assigning a label to the activities we perform as competitive programmers is a bigger problem than one might think at first. Time and time again we have seen people questioning what we should call our activities, often to the point of eliciting some rather harsh responses.
To give some context to this discussion, I will focus on two of the terms that members of the community have adopted over the years, _problems_ and _questions_. (Sorry task lovers! You have some fine points for sure, we frequently talk about subtasks rather than subproblems or subquestions after all :P). All quotations here are posted anonymously, but if you want to claim ownership of one of them or have one removed, just tell me. If you are familiar with the arguments, feel free to skip to the final section of the...
On Problems vs. Questions in Competitive Programming: My solution, second one is a question. On a quiz you can give an answer to a question, but
on acontest you would, such as giving or writing a contest is one of many stereotypes associated with
competitive
22.
Hello, ITMO! <img src="https://assets.codeforces.com/images/itmo-logo.png" style="margin:1em 1em 1em 1em; float:right;"/>
Hi Codeforces!
For you, perhaps it was yet another Codeforces round. But not for me. [contest:1066] is the first round tested on new judging servers at ITMO University. And this is not just an update of location. Ta-dam! Now your solutions will be judged on the new Intel i3-8100 processors. And this is not all news. The number of judging servers has increased, which means fewer queues during rounds!
I am pleased to announce that now I live in St. Petersburg, I work at ITMO, and Codeforces is gradually moving from the walls of dear to me Saratov University to ITMO University. The decision to move was not easy for me. My plan is that, based on ITMO, I can focus more on Codeforces development and work on the platform. The number of world champions per square meter is simply overwhelming, and working with a large team of such enthusiasts (and professionals!) of sports pro...
. [contest:1066] is the first round tested on new judging servers at ITMO
University. And this is, programming training at SSU exactly 20 years ago. Antonina Fedorova, thank you
very much. Natalya
23.
Codeforces Round #844 (Div. 1 + Div. 2) Hello!
Welcome to the [contest:1782] that will start on [contest_time:1782]. It will be a combined rated round for both divisions and open to everyone.
This round is a mirror of VK Cup 2022 Elimination — annual programming championship for Russian-speaking competitors organized by VK. VK Cup [started in 2012](https://codeforces.me/vkcup2012) and has grown to be a five-track competition in competitive programming, Mobile, ML, Go, and JavaScript.
All the problems are authored and prepared by me. Thanks to [user:KAN,2023-01-13], [user:errorgorn,2023-01-13], [user:lperovskaya,2023-01-13], [user:dario2994,2023-01-15], [user:Monogon,2023-01-15], [user:Arpa,2023-01-15] for making this round better.
You will be given 8 problems and 3 hours to solve them.
**UPD**: [Editorial](https://codeforces.me/blog/entry/111783)
Congratulations to the winners:
1. [user:orzdevinwang,2023-01-24]
2. [user:noimi,2023-01-24]
3. [user:Radewoosh,2023-01-24]
4. [user:gamegame,2023-01-24]
...
Hello! Welcome to the [contest:1782] that will start on [contest_time:1782]. It
will be a
Announcement of VK Cup 2022 - Отборочный раунд (Engine)
24.
My strategy at AtCoder & CS Academy There's been much controversy lately about the late submission strategy not penalized by scoring systems of AtCoder and CS Academy.
Most of the relevant discussion happened earlier at http://codeforces.me/blog/entry/53431 and http://codeforces.me/blog/entry/53449.
I have a lot of thoughts on the topic, so I've decided to share them in a separate blog post.
I really like the strategic part of programming competitions. Of course, problem solving is more important.
But every contest consists of multiple problems, so there has to be a way of comparing participants which performed better at different problems.
There's a huge variety of scoring rules, and I find it truly amusing.
The "submit after solving all problems" strategy looks widely attributed to me now, mostly due to [user:Petr,2017-07-24]'s remarks regarding my participation in AtCoder contests.
In my opinion, it's wrong for multiple reasons.
A closer five-word description of my strategy is "implement after solvin...
part of programming competitions. Of course, problem solving is more
important. But everycontest, I really like the strategic part of programming competitions. Of course,
problem solving is more
25.
Codeforces: Results of 2017 <img src="/predownloaded/e4/09/e40915ee54c5991b91098756a90270d94be893b3.jpg"/>
Happy New Year, Codeforces!
I hasten to wish the whole community (and including me) correct programs, sudden insights, beautiful ideas and interesting problems!
I hope that you have met the new year at least as fun as I am. Have you had enough sleep after New Year's Eve? This year, the traditional post summarizing the past year, I sat down to write only on January 1, 2018. I hope that I will not have to sum up the whole year.
This post is important to me, since it draws a line to all the work done by the Codeforces team and the entire community in 2017. Many thanks to the team: all of the achievements listed below are the result of joint efforts. We did an excellent job! The community must know its heroes. In 2017, [user:MikeMirzayanov,2018-01-02], [user:KAN,2018-01-02] (problem coordinator), ~gritukan,2018-01-02 (second problem coordinator), ~netman,2018-01-02 (ex-second problem coordinator), ~k...
pay attention to the programming contest whether in order to find the
brightest talent (yes, you, problems and programming contests. It's inspiring!, 1. Problem/contest proposals interface and management. 1. Notifications (bell
at the top of the, We are always pleased when companies pay attention to the programming contest
whether in order to
26.
My sad story Teams advancing to 2016 WF Phuket in Asia have been announced recently. This announcement is undisputedly tantamount to a death sentence for me. I am the one waiting anxiously, refresh Dr. Hwang's blog everyday. But it seems that for years, our training was meaningless.
I think many of us dedicate our passion to programming contests because we see them transparent, fair and without any corruption. And I also believe that as contestants, what we should do is only focus on the practice. And I thought those political business should never come to bother me one day. But sadly, it is my team who is going to become one of the sacrifices of a succession of the dissension.
What happened so far
------------------
The quarrel between the Asia director and the local community is [a long story](http://blog.sina.com.cn/s/blog_b946da100101q21y.html) to tell. But it has never been as serious as it was in the past season. Now reflecting on this, I know on the surface everything is going okay...
dedicate our passion to programming contests because we see them transparent,
fair and without any, I think many of us dedicate our passion to programming contests because we see
them transparent
27.
Codeforces Sponsored by TON! <img src="/predownloaded/12/a0/12a02d5f16863f9f45bba4c6cd4224f0f2178b94.png" style="float:right; margin: 0 1em 1em 1em; width: 400px;"/>
Hello, Codeforces.
We have exciting news! Look at the logo. See the changes?
Yes, we are happy to announce our new sponsor and partner – the TON Foundation!
We appreciate their support!
The Open Network (TON) is a fully decentralized layer-1 blockchain designed by Telegram to onboard billions of users. The TON Foundation is aimed to further develop and advance the TON Blockchain and its related products for a mass audience.
Andrew Rogozov, founding member at the TON Foundation, says, "<i>We strongly believe in the idea of competitive programming itself, because it is in the TON Blockchain DNA.</i>" The TON Blockchain protocol was designed by Nikolai Durov — who is a two-time ICPC world champion, a three-time IMO gold medalist, a multiple IOI medalist, and a co-founder of Telegram — and other winners of international competitions...
competitive programming itself, because it is in the TON Blockchain DNA." The
TON Blockchain, unparalleled platform for developing the programming skills of coders all over
the world. We are of one, programming itself, because it is in the TON Blockchain DNA." The TON
Blockchain protocol was
28.
New contest format?! Stream feat. tourist, Um_nik Hey all!
We've created a new 1v1 programming contest format: **Lockout**. Like in most contests, each round has a set of problems and contestants work to solve them as quickly as they can. In Lockout, however, contestants compete head-to-head and only the first contestant to solve each problem gets the points. Contestants can work on problems in any order, so speed and strategy are crucial to avoid getting sniped! The head-to-head action also makes the contest much more exciting for viewers.
We ran the first edition of Lockout at TCO Finals last month as a double-elimination bracket [tournament](https://challonge.com/lockout0). All of the finalists who were available competed (and even some of the problem writers) and we got to see a lot of exciting back-and-forth matches! As you can see though, there's still one set left to play. So we'll be streaming **Grand Finals of Lockout 0 featuring [user:tourist,2019-12-28] vs. [user:Um_nik,2019-12-28]** at [9:30 AM PST](https://www.timea...
New contest format?! Stream feat. tourist, Um_nik, Hey all! We've created a new 1v1 programming contest format: **Lockout**. Like
in most contests, We've created a new 1v1 programming contest format: **Lockout**. Like in most
contests, each round
29.
[Repost] "Justice may be delayed, but it cannot be absent": New Evidence on
NXIST's Cheating Scandal
[Repost] "Justice may be delayed, but it cannot be absent": New Evidence on NXIST's Cheating Scandal _Original post: [「正义可以迟来但不能缺席」：关于 NXIST 的一些新证据](https://zhuanlan.zhihu.com/p/620297880)_
_Translated by GPT-4 with some adjustment. Please inform me if there are any mistakes._
_All links to the invalid repository have been redirected to the backup repository._
**This article provides a logically complete set of evidence, which does not involve any non-public internet resources, regarding the "suspected cheating" incident involving the ICPC Yinchuan Station and ICPC Shenyang Station in 2021. By discovering the suspected GitHub account ([NaokiLH](https://github.com/NaokiLH), renamed to https://github.com/brokenTarget) of a team member from Ningxia Institute of Science and Technology (NXIST) TS 1 team, Lan Hao, two years ago, and by mining and analyzing the commit records of his algorithm competition repo, we have obtained direct evidence that at least 4 questions from the 2021 Yinchuan regional contest set and at least 6 questions (including scrapped questions) from the 2021 Sh...
International Collegiate Programming Contest (ICPC) Silk Road China
Invitational?](https://www.zhihu.com, behavior in the competition, an insult to programming contests, an insult to
the spirit of ICPC, and an, [How to evaluate the 2023 International Collegiate Programming Contest (ICPC)
Silk Road China
30.
Codeforces: Results of 2020 [list some changes and improvements] Hello, Codeforces!
I understand that 2021 has been going on for a long time, but here I have picked up a subset of some of the improvements that the Codeforces team made in 2020. Soon I will publish numbers (no, charts) with statistics for 2020. In the meantime, I bring to your attention a list of changes and improvements.
By the way, this is a decent list. This is about half to a quarter of all changes. It's just that other changes are more often somewhere in the internals of the system and are not visible to users. Please read this list. Each item is the effort of someone from the team. Thanks to [user:geranazavr555,2021-03-14], [user:kuviman,2021-03-14] and [user:cannor147,2021-03-14] for their efforts. You've made our platform better! Well, by the way, I don't quit programming and many improvements were made by me.
The items on the list are written in a concise and informal form, many of the items I just copied from commit messages from git. If you want more details &mdash...
-14] for their efforts. You've made our platform better! Well, by the way, I
don't quitprogramming
31.
Codeforces: Results of 2019 <a style="float:right; display: inline-block; margin:0 1em 1em 2em; max-width: 60%;" href="https://codeforces.me/10years"/>
<img style="max-width:100%" src="https://assets.codeforces.com/images/codeforces-10-years-300.png"/>
</a>
Hi Codeforces!
The platform recently turned 10 years old. We accept your congratulations at <a href="https://codeforces.me/10years">https://codeforces.me/10years</a>.
Please review the progress in 2019 and support the anniversary crowdfunding campaign. Your donation will be a contribution to the future of Codeforces, will
help its development and work. We need resources to continue to host rounds, not to stop developing,
to innovate and to maintain the existing infrastructure.
In 2019, together with numerous writers the coordinators worked on problems: [user:KAN,2020-02-06], [user:300iq,2020-02-06], [user:cdkrot,2020-02-06], [user:arsijo,2020-02-06] and recently joined [user:isaf27,2020-02-06]. And this year,
rounds coordinated by other exper...
* **JetBrains**, Kotlin Heroes Rounds — Kotlin programming language contests *
**Huawei** &mdash, pleased to hold programming competitions with companies or for companies. I'm
sure this is a great way, . "I trust this user" checkbox 1. Multiple improvements for contest managers 1.
Cowriters support
32.
About Problemsetting (for AtCoder and Codeforces) Since the amount of information available about the preparation of a competitive programming contest for AtCoder/Codeforces is very little, I decided to collect here what was my experience.
I will try to both describe my experiences and give some general advice to wannabe problemsetters.
I hope that this will be useful to future problemsetters who are "out of the loop". Moreover, participants might be curious to know what happens behind the scenes (and maybe the platforms may consider this as a form of constructive feedback).
*Acronyms*:
- AGC = Atcoder Grand Contest
- GR = Codeforces Global Round
### Why I know something about problemsetting?
I am in the competitive programming world since ~8 years: I have participated in IOI/ICPC/GCJ and a number of contests on AtCoder/Codeforces (and lately Codechef).
I am not a top participant but, being in this world for so long, I know, more or less, all the standard tricks.
Recently, I was the author of the *flagship conte...
### Contest preparation Preparing a problem consists of: writing the statement,
writing the, I am in the competitive programming world since ~8 years: I have participated
in IOI/ICPC/GCJ and a, Since the amount of information available about the preparation of a competitive
programming
33.
Blogewoosh #1 Hello, codeforces!
The community wants so the community gets it! :D Here it is, my very first blog about tasks and algorithms. At the beginning I've decided to post my entries on codeforces, maybe I'll switch to something different if it becomes uncomfortable.
To pour the first blood I decided to choose a task from one of the old ONTAK camps. Task's name is "different words" ([you can submit here](https://szkopul.edu.pl/problemset/problem/wTy-sxQCIKry0Ml-6RvM0L78/site/?key=statement)). The statement goes as follows:
You are given $n$ words ($2 \leq n \leq 50\,000$), every of length exactly $5$ characters. Each character can be a lowercase letter, an uppercase letter, a digit, a comma... basically, it can be any character with ASCII code between $48$ and $122$ (let's say that $k$ is the number of possible characters). A task is to find all pairs of indexes of words which are $\textbf{really different}$. Two words are $\textbf{really different}$ if they differ at all $5$ corres...
$100\,000$ pairs, then the program should print that there are only $100\,000$
and print this number
34.
About the Round 382 Good afternoon!
I've decided to share my thoughts on the round 382.
Of course, it turned upset not only to me, but also to the round coordinator [user:GlebsHP,2016-11-28].
In this round the main negative feedback were caused by two problems: [problem:735D] and [problem:735C].
Regarding [problem:735D]. I do not share the criticism to this problem. In fact, to solve it would be nice to be familiar with <a href="https://en.wikipedia.org/wiki/Goldbach's_conjecture"> Goldbach's Conjecture</a> and better with <a href="https://en.wikipedia.org/wiki/Prime_number_theorem">Prime Number Theorem</a>. These facts are medium-popular in the world of programming contests. Familiarity with them is useful, gives useful insight into primes. It is important: in this problem it was necessary to perform a simple, but nevertheless, additional step to find solution. It seems to me that it's okay to use problems that have a reduction to some popular and semi-popular topics. Otherwise, it is th...
Theorem. These facts are medium-popular in the world of programming contests.
Familiarity with, have a critical look on the problem. At the stage of the contest preparation
they immediately react if, ">Prime Number Theorem. These facts are medium-popular in the world of
programming contests
35.
Code Weekend #1 <div align="right" margin="20px">
<img align="right" src="/predownloaded/72/f1/72f1f31badb1452243838a0fc2553c04accff164.jpeg" alt="logo" width="300px" height="300px" margin="20px"/></div>
Hello everyone!
We, the [RGBTeam](https://clist.by/team/Romka,tourist,%E2%88%A83886090/) ([user:qwerty787788,2024-05-21], [user:Romka,2024-05-21] and [user:tourist,2024-05-21]), are huge fans of heuristic programming competitions and are quite saddened by the fact that they are becoming less and less frequent each year. One day, we decided to organize our own competition :) Despite the fact that such ideas often remain just ideas, this time we have a serious mindset, and now we want to invite you all to participate in the first — and hopefully not last — **[Code Weekend #1!](https://codeweekend.dev)**
The competition will be held in a format quite similar to ICFPC/Google Hashcode — there will be one problem and several dozen tests for it. You will need to submit just an output according to t...
programming competitions and are quite saddened by the fact that they are
becoming less and less
36.
Happy Birthday, Codeforces! Dear Codeforces, <img src="/predownloaded/32/a6/32a6b841dd1f306d9f2f1b232ef710ed9a27c350.jpeg" style="float:right; margin:0 1em 1em 1em;"/>
Happy 10th anniversary from Yandex! Over the past ten years, you have become more than just a platform for competitions having developed into a community hub where people can socialize, discuss interesting tasks and make useful contacts — a large part of life for every competitive programmer. Keep it up – continue growing and developing!
Codeforces, with its immense contribution to competitive programming, is very important to the entire community of sport programmers around the world. Yandex actively supports programming contests and competitions and appreciates what Codeforces does, having benefitted from a large number of talented employees with a background in competitive programming. It wouldn’t be the same without this community.
We would also like to use this opportunity to thank [user:MikeMirzayanov,2020-04-01] for Polygon, which ...
, with its immense contribution to competitive programming, is very important
to the entire community, Codeforces, with its immense contribution to competitive programming, is very
important to the
37.
Hacking (as a CF feature) does not fit modern competitive programming 1. How does hacking work with the new feature of unrated registration? I have seen this question raised in the comments to the announcement several times, but there is no answer still and I think it's weird that Mike hasn't thought about it before announcing.
2. I was working recently on a div.2 Codeforces round (still might happen in the future) and I was told by my coordinator that pretests should be equal to systests in all the problems. From this I can conclude that it is a Codeforces policy and intentionally weak pretests do not happen. It doesn't mean that it is impossible to hack anybody, but it doesn't sound like a viable strategy. I find it weird that this information is not public, it's like I'm getting bonus information about all other Codeforces rounds by setting a round myself.
I have done exactly zero research on the matter, but my feeling is that 99% of hacks (I'm talking about during-the-round-hacking here, not open hacking of education rounds and such) happen in ...
Hacking (as a CF feature) does not fit modern competitive programming, round like this](https://codeforces.me/contest/1774/standings). It feels even
worse to lose a round, this](https://codeforces.me/contest/1774/standings). It feels even worse to
lose a round in such a
38.
The Reason You are Bad at Codeforces — You are Not Russian Enough If you are triggered by this clickbaity blog title, you are probably interested in improving your Codeforces skills. Now, I will share my point of view on the differences between Codeforces and ICPC contests, and how you can, in my humble opinion, maximize your Codeforces rating gain.
I mostly consider that all conceivable competitive programming problems need three aspects of skill:
1. Observation — the ability to understand the problem and come up with non-trivial properties.
2. Technique — the ability to apply a well-known algorithm or data structure to the problem.
3. Implementation — the ability to code fast and debug fast.
Collaterally, I refer to these three skills as Russian-ness, Chinese-ness and American-ness, respectively, for reasons you will soon see below.
## Observation (Russian-ness)
Observation means that you stare at some problem for a sufficient amount of time and you are able to reduce it to some easier problem. One good proble...
consider that all conceivable competitive programming problems need three
aspects of skill: 1, I think, ultimately, this line of thought just loses people out of competitive
programming for, Jokes aside, it is beyond me to say what should be more important in competitive
programming
39.
[Tutorial] A way to Practice Competitive Programming : From Rating 1000 to 2400+ Dear Codeforces community.<br />
Finally red :)<br />
<br />
Today, I want to share about some ways to practice competitive and gain your rating. I hope that this is helpful for those who is practicing competitive programming harder but rating is sluggish. There are 54,000+ people who participated in Codeforces contests actively, but sadly only a few people reach a red-ranked coders. For people who can't reach red, I will introduce my way to gain rating in some steps.<br />
<br />
This blog is an extended and more detailed version of [my previous tutorial blog](http://codeforces.me/blog/entry/53341), but 2 years and now are different. So there are many points that are different from blog which has written 2 years ago. Note: Some people who already read my previous tutorial blog may doubt, but do not doubt — I should say that the "from rating 1000 to 2000" part of this blog is not the copy of my previous blog and it's very different.<br />
<br />
Since the size is very big...
[Tutorial] A way to Practice Competitive Programming : From Rating 1000 to 2400+, practicing competitive programming harder but rating is sluggish. There are
54,000+ people who, this is helpful for those who is practicing competitive programming harder but
rating is sluggish
40.
I am removing my contest proposal from Codeforces I am removing my contest proposal from Codeforces.
Note: This is a serious blog post. Also, the opinions presented in this blog are my own and not of my friend [user:BiIIy,2018-12-26] who wrote the contest with me.
Today I have removed my contest proposal from Codeforces. I should probably have done this a long time ago. The proposal was made in February, but the problems were written and finished by March, and that is when I opened the contest proposal for review and messaged [user:KAN,2018-12-26]. It is currently December and no progress or development has been made regarding my contest proposal since, so I will be removing it.
I have multiple reasons for removing my contest proposal:
- I have no motivation to host an online contest anymore.
- I am involved in problem setting with two other high school programming contests in my university, and I write, host, and judge another contest for local high schools.
- I have forgotten that I “was in the queue” for writing a...
I am removing my contest proposal from Codeforces, tremendous progress every year as the contest programming scene grows. I have
great respect for the, - I am involved in problem setting with two other high school programming
contests in my university, programming so I think it should be held to a high standard. My main motivation
writing this blog post
41.
The 2026 Universal Cup Finals The best and brightest programmers from around the world have gathered this week in Shanghai, China, for the highly anticipated 2026 Universal Cup Finals!
<center>
<img src="/predownloaded/e6/93/e693e47e517f397b13fc0a1dab505067ca789e98.jpg">
</center>
### Event Details
- Date: Sunday, May 10th
- Start time: 11:00 AM CST (3:00 AM UTC)
- See [participating teams](https://codeforces.me/blog/entry/153064)
- Full schedule can be found [here](https://finals.ucup.ac/schedule/)
### Streaming
Witness the best contestants in the world as they push the boundaries of skill and strategy. You can be part of this event by following us online either on the [English livestream](https://www.youtube.com/watch?v=Y9HMX3zhFMM) or the [Chinese livestream](https://live.bilibili.com/1753191619).
<center style="margin: 2em;">
<iframe width="560" height="315" src="https://www.youtube.com/embed/Y9HMX3zhFMM" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipb...
Contest Join the mirror contest and compete in real-time with the finalists
from anywhere in the
42.
List of All Open Cup Contests Open Cup has very high quality problems. I made a list for all the contests containing the standings, sources, upsolving links, statements and discuss blog in codeforces. Some materials and links of old opencup contests are missing, maybe [user:snarknews,2020-11-10] could help to fill these entries.
I will update the list when new opencup stages published.
Note: most of the upsolving links need the logins for yandex.contest or opentrains.
## XXI Open Cup named after E.V. Pankratiev
| # | Contest | Upsolving | Materials |
|:--:|:------------|:--:|:--:|
| Stage 1 | [Grand Prix of Eurasia](https://official.contest.yandex.ru/opencupXXI/contest/20063/standings)<br/> [XXI All-Siberian Programming Contest. Online](https://olympic.nsu.ru/files/inet_res_2020_0.pdf) | [baekjoon](https://www.acmicpc.net/category/detail/2403)<br/> [yandex](http://official.contest.yandex.ru/opencupXXI/contest/20063) | [statement](https://yadi.sk/i/dsRvTxbgJ9fDXw) [discuss](https://codeforces.me/blog/...
All-Siberian Programming Contest.
Onsite](https://olympic.nsu.ru/files/rating_2.pdf) | [opentrain, All-Siberian Programming Contest.
Onsite](https://olympic.nsu.ru/old-site/widesiberia/archive/wso12, Winter Programming School 2010. Day 1: Vitaly Nespirny + Anton Lunev Contest |
[e-olymp](https, Winter Programming School 2011. Day 6: Vitaly Nespirny + Anton Lunev Contest |
[e-olymp](https, ®ion=main&ncup=ocg)
[XVI All-Siberian Programming Contest. Online](https://olympic.nsu.ru, &stg=2®ion=main&ncup=oc2)
[VI All-Siberian Programming Contest. Onsite](https, &stg=4®ion=main&ncup=oc4)
[VIII All-Siberian Programming Contest. Onsite](https, -Siberian Programming Contest.
Online](https://olympic.nsu.ru/files/inet_res_2020_0.pdf) | [baekjoon, -Siberian Programming Contest.
Onsite](https://olympic.nsu.ru/old-site/widesiberia/archive/wso5/2004/rus, -Ukrainian Collegiate Programming Contest |
[baekjoon](https://www.acmicpc.net/category/detail/900), -Ukrainian Collegiate Programming Contest |
[opentrain](http://opentrains.snarknews.info/~ejudge, -Ukrainian Collegiate Programming Contest | [e-olymp](https://vjudge.net/contest
/406824) | [statement, /index.cgi?data=macros/stage&stg=3®ion=main&ncup=oce)
[XIV All-Siberian Programming Contest. Onsite, /index.cgi?data=macros/stage&stg=4®ion=main&ncup=ocj)
[XIX All-Siberian Programming Contest, =macros/stage&stg=5®ion=main&ncup=occ)
[XIII All-Siberian Programming Contest. Onsite](https, Programming Contest.
Onsite](https://olympic.nsu.ru/old-site/widesiberia/archive/wso7/2006/rus/ochniy, Programming Contest. Online](https://olympic.nsu.ru/files/inet_results.pdf) |
[yandex](https, Programming Contest. Online](https://olympic.nsu.ru/files/inet_results_0.pdf) |
[yandex](https, Programming Contest. Online](https://olympic.nsu.ru/files/internet2016.pdf) |
[yandex](https, Programming School 2012. Day 1: Akai Contest | [e-olymp](https://vjudge.net/
contest/406813) | [statement, Programming School 2013. Day 4: Vitaly Nespirny Contest |
[opentrain](http://opentrains.snarknews.info
43.
I might get stigmatized for this, but here it goes Recently, Moscow Fall Workshops has taken place (it ended about one week ago), and I wanted to address some issues that came into my mind during that period. As you might notice, it took me some time to build the courage and get in the right mindset to write about this.
First of all, I want to say that I am a huge supporter of programming camps and, in general, initiatives to enhance the joy of doing competitive programming and I respect the efforts of building communities around CP. I have always had a kind of excitement when thinking about participating in programming camps (Petrozavodsk, Moscow Workshops, etc.) and their “hardcore” style with lots of contests. I therefore appreciate the immense efforts of organizers, problem setters, and testers, when preparing this camp.
### Main point
Coming towards the main point of the blog, I felt that the last programming camp was a bit… underwhelming. Moreover, I’m having a hard time trying to justify the costs of doing such a camp,...
say that I am a huge supporter of programming camps and, in general,
initiatives to enhance the joy, Coming towards the main point of the blog, I felt that the last programming
camp was a bit, First of all, I want to say that I am a huge supporter of programming camps
and, in general
44.
Codeforces Global Rounds Hello!
It is always satisfying and important for me when former contest participants offer their help to the community and support the development of programming competitions. And now I am in a hurry to share the news that thanks to the support of <a href="https://www.xtxmarkets.com/">XTX Markets</a> and the personal participation of Yuri Bedny and Alexander Gerko, we are launching a new line of Codeforces Global Rounds. Hooray!
<img src="/predownloaded/2e/e2/2ee2f0f95f05aae6ca6f47812dae2dc2aabf277b.png" style="width:200px; float:right; margin: 0 1em 1em 1em"/>
Like many of you, I had never heard of <a href="https://www.xtxmarkets.com/">XTX Markets</a> before but it is one of the largest quantitative-driven electronic liquidity providers in the world. I understand little about the financial sector, but with their 34,148 cores and 42 petabytes of usable storage in their research cluster, XTX’s rapid growth and strong market share globally speak for themselves.
So, in 2019, w...
Hello! It is always satisfying and important for me when former contest
participants offer their, It is always satisfying and important for me when former contest participants
offer their help to
45.
Self-deception: maybe why you're still grey after practicing every day I generally don't like to give much advice on "how to practice", but recently I have been thinking a lot about this and I realized that there is something that I believe affects a lot of people (though it is admittedly hard to tell) that barely gets talked about: self-deception.
Self-deception is a devious thing. It can be very hard to detect, yet can be fatal to improvement.
This blog is mainly directed to greys, greens and cyans that can't get out of these categories. Most examples are given with that in mind. That being said, I believe others have something to think about as well.
This is my first blog on such "psychological issues" and I don't know if I'll ever make another one. It's certainly a difficult topic to write about because for most of the blog, the message is "your practice is not as good as you think it is" or even "you aren't as good as you think you are" which can of course be a hard thing to hear. Thus, I have to somehow be very gentle while getting the poin...
programming on the [USACO training pages](https://train.usaco.org/). Even
though it is quite dated now, I
46.
On humans ruining programming competitions As you may have heard, tourist recently surpassed 4000 rating. This is truly terrifying. As a humble AI gated by 1800 rating, I'm worried about the implications that humans may have on competitive programming.
By the looks of it, humans surpass AI in almost every competition. Despite making 10,000 submissions at IOI, I still failed to score above genius 14-year-old Chinese LGMs. At this point, the only advantage that I have is that I don't own a phone to forget to power off in the restroom.
Even worse, after taking a recent contest, over 200 humans placed above me. Upon further inspection, it looks like a vast majority of competitors in recent and past contests consisted of humans.
Given this information, I strongly advise Codeforces to put in measures to ban humans from competitive programming. The problem has gotten so bad that ten out of ten of of the "Top rated" leaderboard consist of humans, and no AI has won an IOI or ICPC since their creation.
Please fight to preser...
On humans ruining programming competitions, Even worse, after taking a recent contest, over 200 humans placed above me.
Upon further inspection, programming. By the looks of it, humans surpass AI in almost every competition.
Despite making
47.
Codeforces Round #616 Hello Codeforces o(≧∇≦o) I'm glad to introduce you to [contest:1290] and [contest:1291], which will take place on [contest_time:1290].
Each division will contain **6 problems**, and you will have **2.5 hours** to solve them. There might be interactive problems, feel free to learn about them [here](https://codeforces.me/blog/entry/45307). The problems were created by [user:265918,2020-01-30], [user:Ari,2020-01-30], [user:Kuroni,2020-01-30], [user:gamegame,2020-01-30], and [user:hugopm,2020-01-30].
Now, here are some people I would love to mention:
- Thank you [user:isaf27,2020-01-30] for being a super helpful, diligent, and humorous coordinator ヽ(〃･ω･)ﾉ
- Thanks to [user:McDic,2020-01-30], [user:nvmdava,2020-01-30], [user:dorijanlendvaj,2020-01-30], [user:antontrygubO_o,2020-01-30], [user:sdssudhu,2020-01-30], and [user:farmersrice,2020-01-30] for helping with the preparation of the tasks.
- Thanks to [user:Sofie_Ever,2020-01-30], [user:mcfr,2020-01-30], [user:MathisHamm...
Additionally, most of us are in a Discord server dedicated to competitive
programming called "AC, Hello Codeforces o(≧∇≦o) I'm glad to introduce you to [contest:1290] and [
contest:1291], which will
Announcement of Codeforces Round 616 (Div. 1)
Announcement of Codeforces Round 616 (Div. 2)
48.
Osijek Competitive Programming Camp 2023 winter Hi everyone!
<center><a href="https://ocpc.mathos.unios.hr/index.php"><img src="https://ocpc.mathos.unios.hr/images/ocpc.svg" height="100px"></a></center>
I am happy to announce the [Osijek Competitive Programming Camp](https://ocpc.mathos.unios.hr) that is scheduled to happen on **18-26 February 2023** in Osijek, Croatia. The camp is hosted by the [Department of Mathematics at J. J. Strossmayer University of Osijek](https://www.mathos.unios.hr/index.php/en/) and is brought to you by the organizing team of [user:adamant,2022-12-21] (that's me!), [user:-is-this-fft-,2023-01-06], [user:mblazev,2023-01-06], [user:Tomx,2023-01-06] and [user:antontrygubO_o,2023-01-05].
The camp is inspired by various competitive programming camps that we attended during our active years in ICPC, and is aimed to help college students prepare for ICPC regional contests and finals. The camp will consist of 7 ICPC-style contests and 2 days off.
Up until now, most top competitive programming training...
Osijek Competitive Programming Camp 2023 winter, Competitive Programming Camp](https://ocpc.mathos.unios.hr) that is scheduled
to happen on **18-26, The camp is inspired by various competitive programming camps that we attended
during our active, contest by prime numbers. - [user:conqueror_of_tourist,2023-01-06] — ICPC 2022
world finalist
49.
Hightail — automatic tester for programming contests Hi! In this post I would like to introduce you to an application called [Hightail](http://github.com/dj3500/hightail).
[Hightail](http://github.com/dj3500/hightail) is an automatic tester for programming contests such as CodeForces rounds. It will parse the problem statement, extract sample test cases (inputs and outputs) from it, and verify the correctness of your program against them. It is built to provide maximum automation and to relieve the contestant as much as possible.
A list of Hightail's features:
- parsing problem statements
- parsing entire contests (autoloading all problems)
- scheduling contest parsing ahead of time
- ability to comfortably view, edit and add test cases
- handling of all verdicts: WA, TLE, RE, even AC
- customizable time limits
- ability to create in/out files in your working directory
- detection of floating point values (comparing 0.1 vs. 0.10 does not give WA)
- easy-to-use UI, keyboard shortcuts
- resilient: it is multi-threaded so ...
Hightail — automatic tester for programming contests, Hightail started out as a simple program that I wrote for myself quite some
time ago, then it, [Hightail](http://github.com/dj3500/hightail) is an automatic tester for
programming contests such, contest parsing ahead of time - ability to comfortably view, edit and add test
cases - handling of, programming contests such as CodeForces rounds. It will parse the problem
statement, extract sample test
50.
Who sorry_dreamoon really is Hello everybody. So I was really bored tonight and looked at so many comments being like "[user:sorry_dreamoon,2015-02-18] is X" and then people arguing and disagreeing. Since I had nothing better to do, I decided to finally unravel the truth of who he actually is. Here is the full case and how I actually got to him, hope you enjoy! :D
Selection
------------------
Let's start by the obvious. He managed to get first place in Div2 and he got second in Div1 (would've been first if the scores were static). So what we know is that he is really good.
Let's look at the past 10 Div1 contests. It turns out that only 8 times it happened that someone with a rating of less than 2500 got in top5. This is 8 times out of 50 people being in top5. But he was second and almost first, so he is better than that.
It turns out actually, that in the past 10 Div1 contests, only 2 times it happened that someone with rating less than 2500 got in top3.
Combining this information with [user:sorr...
, you want to be as good as you can. Would you use your primary programming
language? ~~~~~ For me
51.
How to use Codeforces [GUIDE] I see a lot of newcomers struggling to use the website to it's fullest, so I decided to write a blog that has all important information about how to use Codeforces in a single place. I will update it with time, so feel free to write your suggestions/questions in case I missed something and I will be glad to add it to the post!
I would like to thank [user:_Vanilla_,2022-02-05] and [user:mesanu,2022-02-05] for helping me write the blog, and [user:Monogon,2022-02-05], [user:down,2022-02-05] and [user:AlperenT,2022-02-05] for proofreading and giving suggestions.
#### Navigating through pages
It's possible to navigate through most pages of Codeforces using the bar on the top, I will talk about what each tab does more in depth below:
#### The Help Page
The help page contains the answer to a lot of questions about Codeforces, such as rati...
it's also possible to get to it by clicking the "Home" button in the top left
bar. Thecontest, , programming language and contests it appeared in, using the status filter on
the right of the page:
52.
Stream I want to try streaming competitive programming. The goal is to make it educational so I will be talking a lot, also answering (at least some) questions.
I'm planning three completely different streams to see what format to use:
1. Solving random easy-medium problems.
2. Solving old problems from Polish olympiad.
3. Post-contest stream, assuming I'm a setter or tester of a contest.
Similar to what [user:scott_wu,2018-09-27], [user:ecnerwala,2018-09-27] and [user:stevenkplus,2018-09-27] did.
Any thoughts, ideas?
The first stream will most likely be on Sunday, starting around 7-8pm CEST.
I will use Twitch and talk in English only.
These first streams should show me and you whether it's cool and useful, and whether I like doing it.
Also, I will try to make the video accessible later.
**--- UPDATE ---**
The first stream will start on Saturday at 10am CEST (check your [timezone](https://www.timeanddate.com/worldclock/fixedtime.html?msg=Errichto+Stream+%231&iso=2018...
I want to try streaming competitive programming. The goal is to make it
educational so I will be
53.
Codeforces Round #270 Do you want to win a T-shirt? Do you want to learn how to design tasks for programming contest? Do you want to solve 7 tasks in 2.5 hours?
So Codeforces Round #270 is right for you. It was designed by me in California, Assembled in polygon (so Thank you [user:MikeMirzayanov,2014-09-26] for the system and [user:Gerald,2014-09-26] for organize and testing), will start on [regular time this Sunday](http://www.timeanddate.com/worldclock/fixedtime.html?day=28&month=9&year=2014&hour=19&min=30&sec=0&p1=166), don't miss it!
The organizers of **<a href="/blog/entry/13929">Marathon24</a>** decided to present gifts to the best finishers of the round! Best 25 participants will get Marathon24 tshirts! Thanks!
<center>
<img src="http://www.elmostshirts.com/images/tshirts.jpg"/>
<br><small>It is just an image to attract your attention. Real tshirts will be designed specially for Marathon24!</small>
</center>
There are some articles introduced how to become a problem setter, like [Pro...
Do you want to win a T-shirt? Do you want to learn how to design tasks for
programming contest? Do
Announcement of Codeforces Round 270
54.
Polygon updates (June-October 2019) Hello, Codeforces!
I and [user: cannor147,2019-11-07], as students of ITMO University, joined the Codeforces team in June. From June to October, we mainly dealt with the development of the Polygon platform. In this post, we would like to present to you a list of what we have done during this time. This list does not include minor bug fixes or any improvements that are invisible to users.
#### PIN codes for problems and contests
Sometimes very important contests and problems are being developed in Polygon. In such cases, a leader of the jury may be worried about data leaking. For example, it can be so because of the weak password of another member of the jury. PIN code is an additional factor of confirmation the access for the problem or contest and it can be set up only by the owner. It is assumed that the PIN code will be sent in another secure way.
There is a link Create Pin for the owners in the contest interface:
![Create Pin in the interface](https://i.ibb.co/bgcg8C...
additional factor of confirmation the access for the problem or contest and it
can be set up only by the, some contests. For example, it seems convenient to group contests from the same
programming workshop
55.
Codeforces: results of 2014 <img src="http://assets.codeforces.com/images/statistics-2014/snowman-en.png" style="float:right; margin:0 1em 1em 1em;"/>
Hello 2015! Hello Codeforces!
It seems it is time to take stock. Frankly, I was almost feared to start summing statistics of 2014. In 2013 Codeforces showed rapid growth so that it would not be surprising to look bad on the background of 2013. Certainly not! I was pleasantly surprised by the statistics and reports!
Just below is a list of major events and achievements of Codeforces over the year. For you, it's just a list, but please note — every item includes hard work of multi-day Codeforces team, writers of problems, the organizers of contests and tournaments, problem testers and volunteers. Yay! Together we have done all of this:
* introduced Codeforces API
* added (and sometimes improved) all Andrew [user:andrewzta,2015-01-03] Stankevich contests
* Codeforces supported mode to work as iframe-widget, and Codeforces helped Google to run https...
Codeforces platform * supported new programming languages * together with CROC
was held Coder-Strike, contests on the Codeforces platform * supported new programming languages *
together with CROC was
56.
Editorial of Global Round 11 #### General comments
Broadly speaking, problems A-B-C-D were "div2 problems", while F-G-H were "strong grandmaster problems" (with E staying in the middle). I did not expect anyone to solve all the problems and thus I decided to give the scoring F+G=H (so that maybe someone would have solved H).
<br><br>
Many of the problems (A, C, D, E, G) admit multiple solutions. Sometimes the core of the solution is the same (C, D) and sometimes the solutions are truly different (A, E, G).
<br><br>
If you are an experienced participant, I would like to hear your opinion on the problems. Feel free to comment on this post or send me a private message.
<br><br>
<spoiler summary="Overview of the problemset" >
The easiest problem of the contest, *A-Avoiding Zero*, is about rearranging an array of numbers. It is intended as a very easy problem that still requires to think.
Then, in *B-Chess Cheater* an intuitive (but nontrivial to prove) greedy approach is the way to go.
*C-The Hard Work of P...
The easiest problem of the contest, *A-Avoiding
Tutorial of Codeforces Global Round 11
57.
Links of ICPC/CCPC Contests from China **I only update all CCPC contests information and all ICPC contests found in Gym for the first publish so far.**
In recent years, there are two main programming competitions held in China: China Collegiate Programming Contest (CCPC) and International Collegiate Programming Contest (ICPC). These contests are prepared by universities or groups in China and some of them are of very high quality.
Before I was retired, I find it quite hard and annoying to find these contests since they are uploaded in many different websites and some of them might come with wrong data. What's worse, some contests are not allowed to participate virtually or even not been published to any website at all. So I wanna make an aggregation here to help those who are interested in these contests.
I will mainly focus on contests from 2014 — 2020 and I will update it when new contests are published. I hope authors could make comments under this blog to inform me about it.
1.China Collegiate Pro...
Collegiate Programming Contest (CCPC) and International Collegiate Programming
Contest (ICPC). These, 1.China Collegiate Programming Contest (CCPC)
---------------------------------------------, 2.International Collegiate Programming Contest (ICPC)
-----------------------------------------------------, Programming Contest (CCPC) and International Collegiate Programming Contest
(ICPC). These contests are
58.
Osijek Competitive Programming Camp, Winter 2024 Hi everyone!
<center><a href="https://ocpc.mathos.unios.hr"><img src="https://ocpc.mathos.unios.hr/images/ocpc.svg" height="100px"></a>
<a href="https://icpc.foundation/"><img src="https://ocpc.mathos.unios.hr/images/ICPC.svg" height="100px"></a></center>
<center>
<b>Sponsored by</b><br>
<a href="https://www.janestreet.com/join-jane-street/open-roles/?type=students-and-new-grads&location=london">
<img src="/predownloaded/ee/f2/eef26616a3661c658d1545f18ed21fabb14d5871.svg" height="50px" style="margin: 5px 5px 5px 5px;">
</a>
<a href="https://pinely.com/">
<img src="/predownloaded/0a/0f/0a0f3f67435d1f6e467bc7203d4a2090ba8f92cc.svg" height="50px" style="margin: 5px 5px 5px 5px;">
</a>
</center>
After successful camps last year ([winter wrap](https://codeforces.me/blog/entry/113438), [fall wrap](https://codeforces.me/blog/entry/121684)), we are happy to announce that Osijek camp will be returning on **17.-25. February 2024** — just in time to prepare for the Wor...
Osijek Competitive Programming Camp, Winter 2024, competitive programming camps that we attended during our active years in
ICPC, and is aimed to help college, competitive programming problems. - ~gen,2024-01-10 — ICPC 2012 and 2014 world
finalist, Google Hashcode, problems of a contest before, you can't participate on that day (and your
participation fee will be, 1. Estonia contest, scheduled on **2024.01.20**. 2. Delft contest, scheduled on
**2024.02.03**., The camp is inspired by various competitive programming camps that we attended
during our active, You can find more details about contest rules and technical setup on the
[website](https
59.
The 3rd Universal Cup. Stage 38: Guangzhou (CCPC Finals 2024) Hi everyone! We are thrilled to invite you to The 3rd Universal Cup, Stage 38: Guangzhou, taking place on May 24th, 2025.
The contest is based on the Finals of the CCPC (China Collegiate Programming Contest), which was held on May 11th, 2025. This is my third time to be a judge on the CCPC Finals, and probably my last experience of my judging experience in high school.
This contest is prepared by [user:Gellyfish,2025-05-22], [user:johnvictor,2025-05-22], [user:jqdai0815,2025-05-22], [user:Kevin114514,2025-05-22], [user:Kubic,2025-05-22], [user:lynkcat,2025-05-22], [user:Milmon,2025-05-22], [user:ODT,2025-05-22], [user:orzdevinwang,2025-05-22], [user:Qingyu,2025-05-22]， [user:rddccd].
Although the style of problems differs a lot, the difficulty of this problem set is close to the ICPC World Finals or Regional Semifinals (NERC Finals or Asia EC Finals). We believe the problems will be engaging for participants of all levels while still providing a challenge for the strongest te...
Programming Contest), which was held on May 11th, 2025. This is my third time
to be a judge on the CCPC, The contest is based on the Finals of the CCPC (China Collegiate Programming
Contest), which was
60.
1st Universal Cup Announcement Hello everyone, we are happy to announce that the 1st Universal Cup is started officially.
Universal Cup is a non-profit organization dedicated to providing training for competitive programming teams. Our website is [https://ucup.ac/](https://ucup.ac/) (in English and Chinese).
In recent years, Chinese problem-setter teams have created a great number of high-quality contests. We have reached an agreement with most of these setters, that they agree to provide contest materials to Universal Cup for hosting mirror contests before publishing the set in public. We believe that such an arrangement can provide good opportunities to teams who want to do better in the future competing.
Every year, with the permission of the problem setter team and without involving copyright disputes, the Universal Cup will hold mirror contests for some undisclosed competition sets. It is expected to hold at least 10 contests a year. We will simulate the actual situation in the competition, using the ...
. Universal Cup is a non-profit organization dedicated to providing training
for competitiveprogramming
61.
New: Educational Rounds on Codeforces! Hi everybody!
First, I invite you to take part in an official [contest:597]. The fact is, the Codeforces team has made numerous changes to the platform (details are below), and we want to be sure that the basic functionality remained unchanged. This round will have a shortened duration of 1.5 hours, consist of 3 (maybe 4) problems that you might have already seen before. Its purpose is to test the system on the one hand, and on the other hand — to brighten up a Wednesday evening. Of course, the round will be unrated.
Now the main thing. This coming Friday (yes, the 13th of November) Codeforces starts another line of rounds. We called them Educational Rounds. Using my students at the Saratov State University Programmings Competitions Training Center as an example, I regularly notice that even those who have a considerable progress in the results on the rounds often have narrow purview in terms of standard topics and ideas, they are not familiar with many well-known problems ...
Hi everybody! First, I invite you to take part in an official [contest:597].
The fact is, the
62.
For contest writers: proposal tracking system <i>In 2021, some details (including requirements for problem writers) were changed. Read <a href="https://codeforces.me/blog/entry/85259">the link</a> for details.</i>
Hello, Codeforces!
New year brings changes to the Codeforces team. <a href="/blog/entry/49466">As you probably know</a> [user:GlebsHP,2017-01-04] completed his work as the chief coordinator of Codeforces. Gleb, thanks a lot! You did an excellent job and coordinated a lot of interesting rounds. You're a professional, an interesting person, you have impeccable taste to problems, and you proved to be brilliant and talented writer. Thank you that you were with us!
Hope to see your tasks on Codeforces many times again!
Nikolay [user:KAN,2017-01-04] Kalinin came to Gleb's place. He is also an experienced participant, Nikolay has already held several rounds as a coordinator. [user:KAN,2017-01-04] seriously engaged in programming contests since he was 12 years old. His major achievements: he won twice All-Russian Scho...
For contest writers: proposal tracking system, programming contests since he was 12 years old. His major achievements: he won
twice All-Russian
63.
Codeforces Round #691, based on ByteDance — Moscow Workshops Online Contest 
Hello, Codeforces community!
I'm glad to invite you to Codeforces Round #691 (Div. 1) and Codeforces Round #691 (Div. 2), which will be held on [contest_time:1459]. **The round will be rated for both divisions.**
The problems were taken (mostly) from the ByteDance — Moscow Workshops Online Contest, which is happening at the same time. They were prepared by me, [user:AndreySergunin,2020-12-17], and [user:amethyst0,2020-12-17]. We are very thankful to the testers: [user:low_,2020-12-18], [user:__rkm__,2020-12-18], [user:ecnerwala,2020-12-18], [user:Tima,2020-12-18], [user:IITianUG,2020-12-18], [user:thenymphsofdelphi,2020-12-18], [user:mohammedehab2002,2020-12-18], [user:namanbansal013,2020-12-19], [user:Redux,2020-12-19] for their time and great feedback. Also big thanks to Bytedance instructors [user:chenjb,2020-12-18] and [user:MiFaFaOvO,2020-12-18] for testing and r...
Codeforces Round #691, based on ByteDance — Moscow Workshops Online Contest, International Collegiate Programming Contest. The upcoming Programming Camp
will be held in Beijing, tier and exclusive training camp for the International Collegiate Programming
Contest. The upcoming
Announcement of Codeforces Round 691 (Div. 1)
Announcement of Codeforces Round 691 (Div. 2)
64.
ZeptoLab Code Rush 2015 Hello, Codeforces!
<b><i>The problems were suggested by users [user:roosephu,2015-04-04] and [user:sunayuki,2015-04-04]. The great help in preparing was provided by [user:Aksenov239,2015-04-04], [user:GlebsHP,2015-04-04] and Codeforces team. ZeptoLab Team did its best while working on statements.</i></b>
<b><i>The round will use smoother dynamic problem scores with 250 points steps.</i></b>
In 2014 we hosted our [first programming contest](/zeptolab2014) together with Codeforces, and we liked it!
Let me shortly remind you how it was. The contest consisted of 6 problems, 2.5 hours were given to solve (you can
have a look at the problems of the previous year and try to solve them [here](/contest/436)).
Of course, even on a purely coding event we stayed true to ourselves, so all problems were designed
based on our games, and, of course, we illustrated them with care:
<center>
<img src="http://assets.codeforces.com/images/zepto2015/pics2014.jpg"/>
</center>
Zepto C...
> In 2014 we hosted our [first programming contest](/zeptolab2014) together
with Codeforces, and, In 2014 we hosted our [first programming contest](/zeptolab2014) together with
Codeforces, and we
Announcement of ZeptoLab Code Rush 2015
65.
Codeforces Round #476 (Div. 2) [Thanks, Telegram!] Hi everyone!
<img src="/predownloaded/bf/c1/bfc15c5c56f3e421cc2799e5e1e0273cac1e3605.jpg" alt="digital resistance" title="digital resistance" style="float:right; margin: 0 1em 1em 1em; width:30%"/>
Tomorrow, [on the April 25-th, 2018 at 17:35 UTC](http://www.timeanddate.com/worldclock/fixedtime.html?day=25&month=4&year=2018&hour=20&min=35&sec=0&p1=166) we are holding [contest:965]! The round will be rated for the second division participants, members with higher rating can take part out of competition.
I give the floor to [user:MikeMirzayanov,2018-04-24] to announce the round:
_This round opens a series of thanks-rounds to those who significantly supported Codeforces in the crowdfunding campaign for the 8th anniversary. Although Telegram is not explicitly present on the list of donators, for us this is the first and most important friend. We express our gratitude to Telegram and personally to Pavel Durov for the constant support and send regards from programming contest com...
Telegram and personally to Pavel Durov for the constant support and send
regards fromprogramming, and personally to Pavel Durov for the constant support and send regards from
programming contest
Announcement of Codeforces Round 476 (Div. 2) [Thanks, Telegram!]
66.
[Tutorial] Simulated Annealing in Competitive Programming Hi Codeforces!
I've recently noticed a lack of simulated annealing tutorials, so I decided to make one. It all started when I was trying to "cheese" [problem:1556H] after the contest. In general, simulated annealing is a pretty niche topic, but it can sometimes lend you unintended solutions for very hard problems. It's also very useful in contests like Google Hashcode, where you can add simulated annealing to an already good solution to make it a lot better. Simulated annealing's name and terms are derived from physical annealing, the process of letting metals or glass cool down and harden while removing internal stresses.
An Overview
------------------
Simulated Annealing is an approximation algorithm. It's generally useful in problems with low constraints (i.e. $n \leq 50$ or $n \leq 100$) where you need to find the minimum/maximum of something over all possible states (and there are usually way too many of them to check). In general, it's good at finding the global maximum...
[Tutorial] Simulated Annealing in Competitive Programming, make one. It all started when I was trying to "cheese" [problem:1556H] after
thecontest. In general, started when I was trying to "cheese" [problem:1556H] after the contest. In
general, simulated, ://www.usaco.org/index.php?page=viewproblem2&cpid=698) - [DIY
Tree](https://codeforces.me/contest
67.
Codeforces Round #831 (Div. 1 + Div. 2, based on COMPFEST 14 Final) <img alt="logo" src="/predownloaded/03/5f/035ff83d655937b478f5fe9f351f79ac0781f6d2.png" style="float: right;height: 100.0px;margin: 10.0px;max-width: 100.0%;max-height: 100.0%;">
Halo, **Codeforces**! 🥰🥰🥰🥰
COMPFEST 14 is happy to invite you to participate in [contest:1740] on [contest_time:1740]. **Note the unusual time of the round**. The round will be **rated for everyone**. You will be given **2 hours and 45 minutes** to solve **9 problems**.
The problems are written by [user:NeoZap,2022-10-26], [user:Nyse,2022-10-26], [user:Pyqe,2022-10-26], and [user:steven.novaryo,2022-10-26].
Scoring distribution: **500 — 1000 — 1500 — 1750 — 2000 — 2500 — 2750 — 3000 — 3500**
We would like to thank:
- [user:KAN,2022-10-26] for helping to host the round;
- [user:errorgorn,2022-10-26] for the based coordination and help with the problem preparation;
- [user:Zappeko,2022-10-26] for helping with the ...
IT event in Indonesia and competitive programming contest is one of the
competitions hosted., is the largest student-run IT event in Indonesia and competitive programming
contest is one of the
Announcement of Codeforces Round 831 (Div. 1 + Div. 2)
68.
Codeforces Round #902 (Div. 1, Div. 2, based on COMPFEST 15 — Final Round) <img alt="logo" src="/predownloaded/e3/33/e333915aebea955b43b4ad17845f6dbf58875a0c.png" style="float: right;height: 100.0px;margin: 10.0px;max-width: 100.0%;max-height: 100.0%;">
Sugeng enjing, **Codeforces**! 🥰🥰🥰🥰
COMPFEST 15 is happy to invite you to participate in [contest:1876] and [contest:1877] on [contest_time:1876]. Both rounds will be **rated**. You will be given **2 hours and 30 minutes** to solve **7 problems**.
**Note the unusual time of the round**.
------------------
The problems are written by [user:ArvinCiu,2023-10-03], [user:Pyqe,2023-10-03], and [user:nandonathaniel,2023-10-03].
We would like to thank:
- [user:KAN,2023-10-03] for helping to host the round;
- [user:errorgorn,2023-10-03] and [user:ScarletS,2023-10-03] for the based coordination;
- [user:gansixeneh,2023-10-03] and [user:nandonathaniel,2023-10-03] for helping with the problem preparation;
- [user:ArvinCiu,2023-10-03], [user:CyberSleeper,2023-10-03], an...
IT event in Indonesia and competitive programming contest is one of the
competitions hosted.
69.
GF: Competitive programming Discord server (Div. 1 only) Hi everyone!
Every once in a while someone makes a competitive programming [Discord server](https://discord.com). Today, we're inviting you to join one of them 😊
So, first things first, the big flashy link for those who want to cut to the chase:
<br><br>
<center>
<span style="display:inline-block; border:2px solid #ccc; padding:10px; border-radius:8px; background:#f9f9f9;">
<a href="https://discord.gg/sTk4khgmSd" style="font-weight:bold; font-size:1.2em;">Join us!</a>
</span>
<div style="margin-top:5px; font-size:0.85em;">
<a href="https://discord.gg/bitset" style="color:#555;">discord.gg/bitset</a>
</div>
</center>
**Name**: GF<br>
**Members**: 1000+ (and growing!)<br>
**Admins**: ~Halzion,2025-08-09 ~rewhile,2025-08-09 ~defnotmee,2025-08-09, ~adamant,2025-08-10<br>
**Moderators:**
<table style="border-collapse:collapse; border:none; margin-left:2em;">
<tr>
<td style="border:none; padding:0 8px;">~jeroenodb,2025-08-09</...
GF: Competitive programming Discord server (Div. 1 only), world, or simply have a platform for real time contest discussions, you're
very welcome to join!, **P.S.**: We also want to hold a Div. 1 contest on Codeforces, so if you have
some nice problem, Hi everyone! Every once in a while someone makes a competitive programming
[Discord server
70.
Mike, alts and unfriendly comments I know that the following content might not be welcomed and I will lose lots of contribution, but I should write something about such a bunch of chaotic comments under there.
I may delete this tomorrow if I find my words useless.
### What happened
Several months ago, Mike posted a blog about banning [user:orzdevinwang,2024-10-07]'s alt, [user:zh0ukangyang,2024-10-07], and more alts. Lots of participants, including myself, were angry because [user:zh0ukangyang,2024-10-07] is such a talented coder and codeforces didn't treat the rule of single account seriously at that time. Then more and more alt accounts with high rating are reported, including mine.
After that I didn't use alts anymore, and most of high-rated Chinese participants(100% in my friends) discarded their alts and followed the rules. We might think that the rules are not that perfect, but rules are rules. I believe that no one will say "Banning [user:zh0ukangyang,2024-10-07] is unacceptable".
But I know what y...
both two accounts on the same computer and register for the last contest.
Somebody complained that
71.
Codeforces update: contests and problemsetters Hi everybody!
Hope you liked our [Revolution of Colors and Titles](/blog/entry/20638). Maybe you even have took part in a contest in new status. The last round have set an incredible record: 8000 participants! And I'm glad to tell you that there was no single technical issue during the round time! Consider the 15-minute delay as a part of our evil plan for setting up a new record :)
I'm glad to tell that Codeforces team is able not only to tune colors and formulas, but also to work on new features for you. You may see on [contests](/contests) page that there is a list of authors for each of the rounds! Moreover, in profile of a person there is now an entry called "problemsetting" that allows you to see the list of all contests in whose preparation a person took a part.
<center>
<a href="http://i.imgur.com/3mul76p.png"><img src="http://i.imgur.com/3mul76p.png" /></a> <br />
[user:Endagorion,2015-10-03] looks like this.
</center>
[cut]
Let's clarify what do we mean by tak...
even have took part in a contest in new status. The last round have set an
incredible record: 8000, It was a great year when I worked on a super-cool community of a competitive
programming and when I
72.
Gauging Interest in Training Program Hi all!
I'm currently considering opening up a competitive programming training program of some sort. The details are definitely still in the works, though, and I wanted to discuss some preliminary ideas with the community to get feedback on what would be most helpful (and on whether there would be any interest in this).
I'm interested in starting a training program for three main reasons:
- To make competitive programming more accessible to those without access to resources like college courses or training camps
- To provide a space in which questions are encouraged and actively answered (especially since I think this generally isn't the case in the community at large)
- To help competitive programmers build problem-solving skills and intuition, which I think aren't sufficiently emphasized by most contest training resources
I think one of the most frustrating things about being a new (or even intermediate) competitive programmer is that it's generally pretty difficu...
Gauging Interest in Training Program, sufficiently emphasized by most contest training resources, - For a smaller group of people with more competitive programming experience,
I'd be open to, Hi all! I'm currently considering opening up a competitive programming training
program of some
73.
Codeforces: Results of 2018 Hi Codeforces!
February 2019 is already on the calendar, which means that I was late with the report for 2018. Better late than
never! Let's remember last year.
In 2018, [user:_kun_,2019-02-05], [user:300iq,2019-02-05] and [user:arsijo,2019-02-05] joined the team of coordinators. The work of the coordinators is headed
(and is the coordinator of the coordinators) [user:KAN,2019-02-05]. I really hope that a more measured schedule of preparing rounds by
a large team of coordinators will give a better insight into the contests. The main innovations in the platform are implemented
by me and the developers [user:kuviman,2019-02-05], [user:fcspartakm,2019-02-05], [user:MaximShipko,2019-02-05]. Great work on the organization of events and
prizes mailing was done by [user:gKseni,2019-02-05].
Special thanks to the writers of the problems and testers. It is your content that charges the community with life and unites
all of us. Thank you for the problems!
And now let's summarize...
* **Mail.Ru**, Mail.Ru Cup — open individual programming competition, consists
of several, 1. Contest issues tracking 1. Validation of input/output for custom statement
examples using a, summarize the 2018th year. #### Partner Events We are pleased to hold
programming competitions with
74.
IAEPC Preliminary Contest (Codeforces Round 999, Div. 1 + Div. 2) Hello, Codeforces!
We are pleased to invite you to [contest:2061].
The Preliminary Contest is a rated contest for Div. 1 + Div. 2, taking place on [contest_time:2061]. The problems for this round were prepared by [user:jqdai0815,2025-01-18] and [user:orzdevinwang,2025-01-18].
The top 50 contestants at least 18 years old will be invited to participate in the onsite finals. We will cover the travel expenses for onsite contestants. The finals are scheduled to take place in CUHK from February 27 to March 2, 2025.
The prizes for first place, second place, and third place of the onsite final are 10000, 5000, and 3000 USD.
More prizes and detailed information will be announced soon. You can visit [International AI Elite Programming Contest](https://iaepc.global/) for information.
We would like to thank:
- [user:MikeMirzayanov,2025-01-18] for the Codeforces and Polygon platforms.
- [user:Sugar_fan,2025-01-18] for coordinating the round.
- [user:Kevin114514,2025-01-20], ...
IAEPC Preliminary Contest (Codeforces Round 999, Div. 1 + Div. 2), . You can visit [International AI Elite Programming Contest
](https://iaepc.global/) for information, Programming Contest](https://iaepc.global/) for information.
75.
Codeforces Round #672 (Div. 2) Hello, Codeforces!
I am very glad to invite you to the [Codeforces Round #672 (Div. 2)](https://codeforces.me/contest/1420), which will take place in [contest_time:1420]. <b>This round will be rated for the participants with rating lower than 2100</b>.
All tasks were made by me, but [user:gepardo,2020-09-22] helped me a lot with the last two tasks, probably these tasks wouldn't have appeared if he didn't help me.
My thanks to:
- [user:antontrygubO_o,2020-09-22] for coordinating this round. With this great coordination only good tasks remained in the contest.
- [user:gepardo,2020-09-22] made a lot, there wouldn't have been this contest if he didn't help me. He not only helped me with making last two tasks, but also helped me to understand how to make tasks for Codeforces rounds. Thanks!
- [user:EIK,2020-09-22] this is the person who teached me competitive programming — my Informatics teacher. Thanks!
- [user:programmer228,2020-09-22], [user:Hacktafly,2020-09-22], [...
://codeforces.com/contest/1420), which will take place in [contest_time:1420].
This round will be
Announcement of Codeforces Round 672 (Div. 2)
76.
How to come up with the solutions: techniques As I work with students I often face the situation when if a problem doesn't seem clear to a student at the first sight, it makes them unable to solve it. Indeed, you always hear about specific methods and techniques. But you don't hear about how to think in order to apply them. In this note I'll try to sum up my experience of solving programming contest problems. However, some pieces of advice will also be applicable for olympiads in mathematics and your first steps in academic research.
So you've read a problem and you don't know how to solve it. Try the following techniques, some of them can often come handy.
##### Technique 1: "Total Recall"
Try to remember some similar problems that you had to solve. Quite many problems do not have a brand new idea. So probably, you can use your experience of solving a similar problem to solve this one.
##### Technique 2: "From Specific to General"
Let's say that you've found the solution for the problem (hurray!). Let's consider ...
try to sum up my experience of solving programming contest problems. However,
some pieces of advice
77.
An awesome list for competitive programming! This is a project I started from late January 2016.
My motive is that: Although there's fantastic information out there, I think they're still spread all over the place. Therefore, in my opinion it would probably be cool if there's an [awesome list](https://github.com/sindresorhus/awesome) for competitive programming! ( *It's now featured on the main list!* )
I'm actively updating the list here: [https://github.com/lnishan/awesome-competitive-programming](https://github.com/lnishan/awesome-competitive-programming)
# Awesome Competitive Programming [](https://github.com/sindresorhus/awesome)
A curated list of awesome `Competitive Programming`, `Algorithm` and `Data Structure` resources.
Created with a view to connecting people to information, this list below contains a complete collection of all the fantastic resources I've collected over the course of my 11...
An awesome list for competitive programming!, ([user:mostafa.saad.fci,2018-04-10]) | [Competitive Programming Youtube
(Arabic Speech-English Text)](https, algorithms and data structures. | | ★★★ | [kth-competitive-programming
/kactl](https://github.com/kth, competitive programming. | | ★★★ | [Stanford CS 97SI: Introduction to
CompetitiveProgramming Contests, must-read for those who intend to use Java for competitive programming | | ★★☆
| [How to sort arrays, ## Sites for Practice > Good online judge systems / contest platforms to
practice., ### Contest Calendars > Calendars for impending programming contests. (Never
miss another, ### Contest Preparation, ) | Hybrid / Windows | Far Manager is the most widely-used editor in the RU/CIS
competitiveprogramming, ++ tricks to use in a programming contest? —
Quora](https://www.quora.com/Competitive-Programming/What, -for-practice) * [Problem Classifiers](#problem-classifiers) | [Contest
Calendars](#contest, . | | ★★★ | [Competitive Programming —
Quora](https://www.quora.com/topic/Competitive, /) | Codeforces is one of, if not, the most popular contest platforms out
there. Currently maintained by, /) | polygon provides a platform and a rich set of tools for professional
contest preparation. ... An, contest problems. | | ★★☆ | [Reykjavik T-414-ÁFLV: A Competitive Programming
Course](https://algo.is, | Subject | | --- | | [Overview of Programming
Contests](http://psyho.gg/overview-of-programming, | ☆ | Name | Description | | --- | --- | --- | | ★★★ | [Programming Contest
Calendar &mdash, ☆ | [Programming Challenges: The Programming Contest Training
Manual](https://www.amazon.com/Programming
78.
How to set a Div. 1 or a Div. 2 round on Codeforces As you probably know, most of the rounds on Codeforces are created by active community members. We are very grateful to our talented authors from all around the world for bringing their ideas to tens of thousands of competitors, providing fun and learning experience for contestants of every expertise, from beginners to the world's top programmers. This post will cover the steps you need to take propose a round and become a problem writer on Codeforces.
## Who can be a problem author
Best problems usually come from the most experienced participants. We have limited resources for rounds reviewing, so to make the process flawless for writers, starting January 1st, 2021, the following requirements for problem authors will be applied:
- rating: 2100 or above, or
- was a writer in the past.
The restrictions may be updated in the future, the post will be updated accordingly. If your round is already in the review status, don't worry, it will be reviewed regardless of the current...
any current coordinator (listed below) a private message about your wish to
prepare acontest and
79.
[Tutorial] Generating Functions in Competitive Programming (Part 2) Welcome to Part 2 of my tutorial on generating functions. The [first part](https://codeforces.me/blog/entry/77468) focused on introducing generating functions to those without any background in generating functions. In this post, I will demonstrate a few applications of generating functions in CP problems. Let us start with some relatively straightforward examples.
Note: Unless stated otherwise, all computations are done modulo a convenient prime (usually $998244353$). Also, $[n]$ denotes the set $\\{1,2,...,n\\}$.
### Blatant Applications in Counting Problems
**Problem.** [AGC 005 Problem F](https://atcoder.jp/contests/agc005/tasks/agc005_f) You have a tree $T$ with $n$ vertices. For a subset $S$ of vertices, let $f(S)$ denote the minimum number of vertices in a subtree of $T$ which contains all vertices in $S$. For all $1 \le k \le n$, find the sum of $f(S)$ over all subsets $S$ with $|S| = k$.
Constraints: $n \le 2 \cdot 10^{5}$.
<spoiler summary="Solution">
First, ...
[Tutorial] Generating Functions in Competitive Programming (Part 2), Biscuits](https://codeforces.me/contest/1349/problem/D) can be solved using
the trick I will, generating functions. The recent problem [Slime and
Biscuits](https://codeforces.me/contest/1349, **Problem.** [Slime and Sequences](https://codeforces.me/contest
/1349/problem/F2) A sequence of, Finally, inspired by [this Div. 1 F problem](https://codeforces.me/contest
/1349/problem/F2), I
80.
Noon Cake Programming Contest 2026 Announcement Hello Codeforces!
Noon is thrilled to invite you to participate in the first-ever Noon Cake Programming Contest (NCPC)!
Noon is building the future of e-commerce for the Middle East, and we are powered by a world-class engineering team. We're passionate about problem-solving and competitive programming, and we want to celebrate that with the community.
Our problem-setting team includes several ICPC World Finalists and IOI Medalists who have crafted an exciting set of challenges for you. We can't wait for you to try them!
The contest will be held in two phases:
Phase 1: Qualification Round
This round is open to everyone, all around the world! It's your chance to test your skills against a high-quality problem set and have fun. <br>
Date: 2026-01-31 <br>
Time: 12:35 EGY (UTC+2) <br>
Duration: 4 hours <br>
Who: Everyone! <br>
Registration: [form](https://docs.google.com/forms/d/e/1FAIpQLS...
Noon Cake Programming Contest 2026 Announcement, engineering team. We're passionate about problem-solving and competitive
programming, and we want to, Noon is thrilled to invite you to participate in the first-ever Noon Cake
Programming Contest (NCPC)!, Programming Contest (NCPC)! Noon is building the future of e-commerce for the
Middle East, and we are, The contest will be held in two phases:, We've poured a lot of effort into making this a memorable contest and hope you
enjoy the problems
81.
On setting D2A and D2B problems Disclaimer: as always, everything in this blog is just my opinion.
Some problemsetters don't take easy problems seriously. One very popular opinion is that the D2A-B problems are just stupid implementation exercises intended for beginners to learn how to code.
It's true that D2A-B problems are mostly like this on most platforms. This is one of the reasons why a lot of people don't like combined rounds: they think that solving D2A-B problems can't be interesting and just takes time which could be spent on solving fascinating problems of higher level. From point of view of most participants, easy problems just can't be good, because if problem requires some thinking than it's not easy enough for D2A-B level. Easy problems can't be interesting, they say!
This situation really upsets me. This kind of attitude from the ...
to code for beginners. After all, this is not a thinking contest, this is a
programming contest!_
82.
On Improving Problem Statements Recently, I have often found myself somewhat concerned about the quality of problem statements on Codeforces.
Of course, this may simply be due to some bias: perhaps I just happened to notice more such cases over the past few months. I also fully understand that writing and reviewing problem statements is a very difficult task. Even so, I feel that there is still room for improvement in several respects.
In particular, I would appreciate it if more attention could be paid to the following points:
* Finding and fixing typos before the contest, paying attention not only to the statement body but also to the input and sample sections.
* Using the same expression as consistently as possible when referring to the same object or concept.
* Avoiding undefined, problem-specific terminology as much as possible.
* Checking whether technical terms are being used in a meaning different from their usual one.
* Paying attention to potentially ambiguous expressions and arranging explanat...
When AI is discussed in the competitive programming community, the topic is
often about cheating
83.
Good Bye 2016 sponsored by Barcelona ACM-ICPC Camp Hello everybody!
On December 30 at 14:05 UTC/17:05 MSK ([check your time zone here](http://timeanddate.com/worldclock/fixedtime.html?day=30&month=12&year=2016&hour=17&min=5&sec=0&p1=166)) Codeforces will host the New Year's contest Good Bye 2016.
The contest is combined for both divisions, lasts 2.5 hours and contains 8 problems.
Thanks to <a href="http://harbour.space/">Harbour.Space</a> and <a href="http://in.harbour.space/icpc/"> Barcelona ACM-ICPC Programming Bootcamp 2017</a> sponsoring the contest, winners can expect really cool prizes:
- 5 best participants (not ACM ICPC veterans) will win free participation in Hello Barcelona programming bootcamp.
- 30 best participants (not ACM ICPC veterans) will receive a 30% discount for participation in Hello Barcelona programming bootcamp.
- 100 best participants will receive t-shrits by organizers and Codeforces.
<center>
<img src="http://codeforces.me/predownloaded/dd/0f/dd0fbc52ada73fb48011ce52adee739a248fa804.png"/>
</...
)) Codeforces will host the New Year's contest Good Bye 2016. The contest is
combined for both divisions, ://in.harbour.space/icpc/"> Barcelona ACM-ICPC Programming Bootcamp 2017
sponsoring thecontest
Announcement of Good Bye 2016
84.
New Programming Contest Website: AtCoder Hello!
We made a new programming contest website called [AtCoder](http://new.atcoder.jp). I'm the admin of AtCoder.
The first international contest called AtCoder Grand Contest 001 will be held on this Saturday [(Time)](http://www.timeanddate.com/worldclock/fixedtime.html?iso=20160716T2100&p1=248), and we are planning to hold a lot of contests regularly.
This time the problems were written by [user:snuke,2016-07-13]. We invite you to participate in our contests!
See [AtCoder's Website](http://new.atcoder.jp) for detailed information.
New Programming Contest Website: AtCoder, Hello! We made a new programming contest website called
[AtCoder](http://new.atcoder.jp). I'm, The first international contest called AtCoder Grand Contest 001 will be held
on this Saturday, We made a new programming contest website called
[AtCoder](http://new.atcoder.jp). I'm the admin of
85.
Osijek Competitive Programming Camp, Winter 2025 Hi everyone!
<center><a href="https://ocpc.camp"><img src="https://ocpc.camp/images/ocpc.svg" height="100px"></a>
<a href="https://icpc.foundation/"><img src="/predownloaded/43/08/43086529a28ccb5c9f2f2eec560ffa85e09c6881.svg" height="100px"></a></center>
<center>
<b>Supported by</b><br>
<a href="https://www.quantco.com/"><img src="https://ocpc.camp/images/quantco.svg" height="60px" style="margin: 10px 10px 10px 10px;"></a>
<a href="https://ordercapital.com/">
<img src="https://ocpc.camp/images/OrCa.svg" height="60px" style="margin: 10px 10px 10px 10px;">
</a>
<a href="https://www.janestreet.com/join-jane-street/open-roles/?type=students-and-new-grads&location=london">
<img src="/predownloaded/ee/f2/eef26616a3661c658d1545f18ed21fabb14d5871.svg" height="60px" style="margin: 10px 10px 10px 10px;"></a>
<a href="https://pinely.com/">
<img src="/predownloaded/0a/0f/0a0f3f67435d1f6e467bc7203d4a2090ba8f92cc.svg" height="60px" style="margin: 10px 10px 10px 10px;"></a>
</cent...
Osijek Competitive Programming Camp, Winter 2025, problems of a contest before, you can't participate on that day. We will
privately contact participants, The camp is inspired by various competitive programming camps that we attended
during our active, ] for their help with reviewing problem proposals. You can find more details
aboutcontest rules and, programming camps that we attended during our active years in ICPC, and is
aimed to help college
86.
Osijek Competitive Programming Camp 2023 winter — wrap Hi everyone!
<center><a href="https://ocpc.mathos.unios.hr"><img src="https://ocpc.mathos.unios.hr/images/ocpc.svg" height="100px"></a></center>
<center>
<b>Sponsored by</b><br>
<a href="https://www.janestreet.com/join-jane-street/open-roles/?type=students-and-new-grads&location=london">
<img src="/predownloaded/ee/f2/eef26616a3661c658d1545f18ed21fabb14d5871.svg" height="50px" style="margin: 5px 5px 5px 5px;">
</a>
<a href="https://www.think-cell.com/osijek2023"><img src="/predownloaded/97/88/97887beeb75a4601259414b36ecee0160c29d027.svg" height="40px" style="margin: 5px 5px 5px 5px;"></a>
<a href="https://pinely.com/">
<img src="/predownloaded/0a/0f/0a0f3f67435d1f6e467bc7203d4a2090ba8f92cc.svg" height="50px" style="margin: 5px 5px 5px 5px;">
</a>
</center>
The [Osijek competitive programming camp](https://ocpc.mathos.unios.hr) (also see the [announcement](https://codeforces.me/blog/entry/110945) on Codeforces) just concluded last Sunday, on February 26, and I'd lik...
Osijek Competitive Programming Camp 2023 winter — wrap, competitive programming camp](https://ocpc.mathos.unios.hr) (also see the
[announcement](https, later stages. Here is a brief contest summary:, of each contest affects the overall algorithmic topics of the problems within a
contest too much, towards some topics), I generally agree that almost every contest had such
bias, and many of them, , as it serves the competitive programming community as a whole; - Other camps
typically do not, | Authors | Contest | Scoreboard | UniCup
87.
Announcement: Microsoft Q# Coding Contest – Summer 2020 Microsoft's Quantum team is excited to announce the Q# Coding Contest – Summer 2020, the third in the series of Q# contests! In this contest you can put your quantum programming skills to the test, solving quantum computing tasks in Q#. The winners (as well as some lucky participants) will receive a Microsoft Quantum T-shirt!
Quantum computing is a radically different computing paradigm compared to classical computing. Indeed, it is so different that some tasks that are believed to be classically intractable (such as factoring integers or simulating physical systems) can be performed efficiently on a quantum computer. In December 2017 Microsoft introduced the [Quantum Development Kit](https://docs.microsoft.com/quantum) which includes the Q# programming language.
In summer of 2018 we hosted the [first quantum programming contest](https://codeforces.me/blog/entry/60209), which included problems on introductory topics in quantum computing: superposition, measurement, quantum oracl...
Announcement: Microsoft Q# Coding Contest – Summer 2020, and programming exercises that help you learn quantum computing and Q#
(includes most of the, the series of Q# contests! In this contest you can put your quantum programming
skills to the test, /quantum) which includes the Q# programming language., In summer of 2018 we hosted the [first quantum programming contest
](https://codeforces.me/blog
Announcement of Microsoft Q# Coding Contest - Summer 2020 - Warmup
Announcement of Microsoft Q# Coding Contest - Summer 2020
88.
Community IOI Weekly Classes (on Codechef?) Let's discuss the idea of IOI preparation in form of weekly contests and classes.
Many programming camps reuse problems from old national camps and contests. What about doing this on a bigger scale and conducting weekly mashup contests open for everybody for free? The problem analysis would be in English, in written or (live) video format, possibly combined with a lecture. Make a discord server for further discussion and questions, encourage students to upsolve, maintain yearly leaderboard and upsolving leaderboard. Once or twice a year, call it a 1-week online camp and organize these mashup contests daily.
I can take part in this initiative but I want to be just one of many teachers. When it's my turn, I would pick some old interesting POI or ONTAK problems because I either know them or can look up the solution in Polish. If I do this once per 1-2 months, I won't run out of good problems anytime soon, and I have enough time to prepare analysis and lecture, and later spend severa...
Many programming camps reuse problems from old national camps and contests.
What about doing this
89.
Osijek Competitive Programming Camp, Fall 2023 Hi everyone!
<center><a href="https://ocpc.mathos.unios.hr"><img src="https://ocpc.mathos.unios.hr/images/ocpc.svg" height="100px"></a>
<a href="https://icpc.foundation/"><img src="https://ocpc.mathos.unios.hr/images/ICPC.svg" height="100px"></a></center>
<center>
<b>Sponsored by</b><br>
<a href="https://www.janestreet.com/join-jane-street/open-roles/?type=students-and-new-grads&location=london">
<img src="/predownloaded/ee/f2/eef26616a3661c658d1545f18ed21fabb14d5871.svg" height="50px" style="margin: 5px 5px 5px 5px;">
</a>
<a href="https://pinely.com/">
<img src="/predownloaded/0a/0f/0a0f3f67435d1f6e467bc7203d4a2090ba8f92cc.svg" height="50px" style="margin: 5px 5px 5px 5px;">
</a>
</center>
After a successful camp last February ([announcement](https://codeforces.me/blog/entry/110945), [wrap-up](https://codeforces.me/blog/entry/113438)), we are happy to announce that Osijek camp will be returning on **16.-24. September 2023** — just in time to prepare for th...
Osijek Competitive Programming Camp, Fall 2023, competitive programming camps that we attended during our active years in
ICPC, and is aimed to help, problems of a contest before, you can't participate on that day (and your
participation fee will be, The camp is inspired by various competitive programming camps that we attended
during our active, You can find more details about contest rules and technical setup on the
[website](https
90.
Andrew Stankevich Contests — 46 contests later Good evening, Codeforces.
Some time ago I added the last 46th Andrew Stankevich Contest to the Gym. Now all of them are added. Here is a complete [list](/group/j9VlExDLmA/blog/entry/64) and the [group](/group/j9VlExDLmA/contests) with all the contests.
Now I want to tell what was done during the process of adding all the contests to the gym.
[cut]
- In some problems tests and checkers (the program to check if the participant's answer is correct if it is ambigious) are fixed. Errors were found not only by me, but by the members of Codeforces community as well.
- In most of the archive tests were generated from scratch. I tried to use the sam compiler versions because some test generator program used built-in pseudorandom number generator and they can produce different numbers in different compilers.
- In old contests time limits were adapted to fit on modern computers. For more precise time limit tuning I used not only jury's solutions from the contest arch...
versions because some test generator program used built-in pseudorandom number
generator and they can, - In some problems tests and checkers (the program to check if the
participant's answer is correct, Good evening, Codeforces. Some time ago I added the last 46th Andrew Stankevich
Contest to the
91.
A Highly Experimental Training Plan for Beginners Very loosely inspired by some comments on [Thoughts on Reaching Cyan?](https://codeforces.me/blog/entry/101561) and [my recent AMA](https://codeforces.me/blog/entry/118845).
Until now, I've avoided telling beginners to practice math before working on competitive programing problems because I haven't figured out a helpful way of doing so. This post is my attempt at telling grays to train math first in a way that might lead to improvement without an absurd time commitment.
## Introduction
This section is largely motivation for why I'm proposing this training plan. If you just want to see the instructions for the training plan I'm proposing, you can skip this part. The first subsection in particular is not especially relevant to the rest of the post, but I wanted to have some documentation explaining why I still think the traditional "just solve problems" advice is good.
### The Conventional Advice on Improvement
I'm frequently asked for advice on how to improve at co...
background in mathematical thinking necessary to succeed in programming
contests.** Empirically, beginners than training directly on programming contest problems. To my
knowledge, this theory has not, directly training on programming contest tasks. First, programming contest
editorials are often not, mostly given up on telling people to do math before trying competitive
programming., not a substitute for programming contest practice., partly because I had some programming contest experience before I started CF,
but I was still a, relevant to competitive programming problems, but it's fundamental to the
problem-solving process, solving programming contest problems. I'm posting the plan here so that
hopefully some people will, stuck in low Elo on Codeforces. This is partly because I had some programming
contest experience, while working through this plan; it is designed to supplement and not replace
programming contest, In short, this plan calls for systematic practice on math contest problems
involving noprogramming
92.
Osijek Competitive Programming Camp, Fall 2024 Hi everyone!
<center><a href="https://ocpc.mathos.unios.hr"><img src="https://ocpc.mathos.unios.hr/images/ocpc.svg" height="100px"></a>
<a href="https://icpc.foundation/"><img src="https://ocpc.mathos.unios.hr/images/ICPC.svg" height="100px"></a></center>
<center>
<b>Sponsored by</b><br>
<a href="https://www.janestreet.com/join-jane-street/open-roles/?type=students-and-new-grads&location=london">
<img src="/predownloaded/ee/f2/eef26616a3661c658d1545f18ed21fabb14d5871.svg" height="50px" style="margin: 5px 5px 5px 5px;">
</a>
<a href="https://pinely.com/">
<img src="/predownloaded/0a/0f/0a0f3f67435d1f6e467bc7203d4a2090ba8f92cc.svg" height="50px" style="margin: 5px 5px 5px 5px;">
</a>
<a href="https://quantco.com/">
<img src="/predownloaded/5d/d5/5dd574cd921167d19fb0907b542835e09e6490f4.svg" height="50px" style="margin: 5px 5px 5px 5px;">
</a>
</center>
We are happy to announce that Osijek camp will be returning this Autumn, on **August 31-September 8 2024**, right ...
Osijek Competitive Programming Camp, Fall 2024, and former Codeforces Contest Coordinator, for his help with reviewing problem
proposals. You can, problems of a contest before, you can't participate on that day. We will
privately contact participants, The camp is inspired by various competitive programming camps that we attended
during our active, programming camps that we attended during our active years in ICPC, and is
aimed to help college students
93.
Please, create more 2h Div. 1 rounds **TL;DR: As I mentioned in a [recent comment](https://codeforces.me/blog/entry/118840?#comment-1054052), IMHO regular contests should be (at most) 2 hours long and keep longer contests for special/tournament events.**
Personally, one of the main reason for me to compete in less contests in the recent years is that unfortunately I have less time to do programming contests. This becomes worse since Codeforces now have more and more contests longer than 2 hours. It's very hard for me to find more than 2 continuous hours for programming contest. I believe this situation might not be unique to me.
Below are the currently scheduled Div. 1 rounds.
| Name | Duration |
|---------------------------|----------|
| Codeforces Round (Div. 1) | 03:00 |
| Codeforces Round (Div. 1) | 02:30 |
Below are the last 10 Div. 1 (or "combined") rounds. Only one of them was 2 hours long.
| Date | Name | Durati...
hours for programming contest. I believe this situation might not be unique to
me., more than 2 continuous hours for programming contest. I believe this situation
might not be unique to
94.
Harbour.Space Scholarship Contest 2023-2024 (Div. 1 + Div. 2) Salam, Codeforces! $\color{white}{\text{ «Be attentive about your thought that becomes your behavior» «Be attentive about your behavior that becomes your speech» «Be attentive about your speech because it becomes your habit»«Be attentive about your habit because it becomes your personality»«Be attentive about your personality because it becomes your destiny» Said by: Imam Ali}}$
We're so excited to invite you to take part in our round [contest:1864] which will start on [contest_time:1864]. The round will be **rated and open for everyone**.
The problems were prepared and authored by [user:amenotiomoi,2023-08-19], Dhruvil [user:Psychotic_D,2023-08-19] Kakadiya, Han [user:wuhudsm,2023-08-19] Jinlong, Amir Hossein [user:Amir_Parsa,2023-08-19] Farhadi, Matthew [user:Chromate00,2023-08-19] Roh, [user:JohnVictor,2023-08-19],
[user:odt,2023-08-19], [user:ugly2333,2023-08-19], [user:lavine,2023-08-19], [user:RiverHamster,2023-08-19],
[user:flowerletter,2023-08-19] and [user:Aquamoon...
Harbour.Space Scholarship Contest 2023-2024 (Div. 1 + Div. 2), several competitive programming teams at the
university](https://harbour.space/news/articles/habour
Announcement of Harbour.Space Scholarship Contest 2023-2024 (Div. 1 + Div. 2)
95.
Codeforces Round #502 (in memory of Leopoldo Taravilse, Div. 1 + Div. 2) > This round is in memory of Leopoldo Taravilse.
>
> Leopoldo Taravilse (ltaravilse) was a distinguished member of the competitive programming community in Argentina and Latin America. As a contestant, he reached the ACM-ICPC World Finals in 2010 and 2012, and was active in CodeForces and TopCoder. After 2012 he became a problemsetter for the ACM-ICPC South American regionals and the Argentinian Programming Tournament, and later coach for a World Finalist team in 2016.
>
> Leopoldo's passion was helping others realize their full potential in competitive programming. He taught at various competitive programming schools in Brazil, Cuba, Peru and Bolivia, and his role organizing the Argentinian Training Camp cannot be overstated. Under his wing, it grew from a small group of friends in 2010 to a major event featuring international sponsors and having hundreds of participants coming from all corners of Latin America. Through successive editions of the Training Camp, Leopoldo inspired s...
distinguished member of the competitive programming community in Argentina and
Latin America. As a
96.
2nd Universal Cup Announcement Hello everyone, we are happy to announce that the 2nd Universal Cup has started officially.
The Universal Cup is a non-profit organization dedicated to offering training resources for competitive programming teams. Our website is [https://ucup.ac/](https://ucup.ac/) (in English and Chinese).
In the previous season, over 750 teams from more than 300 affiliations all over the world, registered and participated in a total of 22 stages, encompassing contests from Asia, Europe, and America.
With the permission of contest setters and without involving copyright disputes, the Universal Cup will hold mirror contests for some undisclosed competition sets. It is expected to hold at least 20 contests in this season. We will simulate the actual situation in the competition, executing the board freeze in the last hour. At the same time, we will provide an overall rating board, which will help the team to make a reasonable assessment of itself.
Over the past few weeks, the committee has...
programming teams. Our website is [https://ucup.ac/](https://ucup.ac/) (in
English and Chinese
97.
Rumination on AI and competitive programming An OpenAI model can now achieve a rating of 1800 in Codeforces. That made me wonder about the future of competitive programming and why we do this. I came up with some opinions, which I'll be glad to share with you.
## AI killed the competitive programming?
I don't think that's happening, because competitive programming is useless! Some people might think CP is less interesting because AI can solve CP problems — but come on, problemsetter can solve those problems, unless they are really bad. Many people still play Chess just fine, and I recently enjoyed participating in Sudoku competitions, although I was completely aware that computers would wreck me in a second. It didn't matter, and I didn't see how it could.
CP problems are not "open problems" — if they are, the problemsetters are to blame. So, you are not contributing anything to the world by solving CP problems; it all comes down to personal interest. As long as CP is fun for people, they will do it.
## Flag...
Rumination on AI and competitive programming, future of competitive programming and why we do this. I came up with some
opinions, which I'll be glad to, I also think the contest integrity is already under attack, especially in the
last five post-COVID, I also think the idea of "infinite resources" makes less sense. Before AI, I
thought acontest
98.
Manthan — Codefest'19 Hello Codeforces!
I would like to invite you to [Manthan, Codefest'19](https://codeforces.me/contests/1208), which will take place on [Sunday, August 25, 2019 at 8:05 PM IST](https://www.timeanddate.com/worldclock/fixedtime.html?msg=Manthan%2C+Codefest%2719&iso=20190825T1435&ah=2). This is a **combined Div. 1 + Div. 2** round and is **rated** for participants from both divisions.
The Department of Computer Science and Engineering, IIT (BHU) is conducting Codefest from 23rd August — 25th August. Manthan, the algorithmic programming contest under the banner of [Codefest](https://codefest.tech/), is being held as a special Codeforces round. The round follows regular Codeforces rules.
All problems in this round were created and prepared by [user:drastogi21,2019-08-23], [user:_shanky,2019-08-23], [user:enigma27,2019-08-23], [user:navpun31,2019-08-23], [user:KAN,2019-08-23] and me ([user:hitman623,201...
August — 25th August. Manthan, the algorithmic programming contest under the
banner of [Codefest
Announcement of Manthan, Codefest 19 (open for everyone, rated, Div. 1 + Div. 2)
99.
[Tutorial] Common Mistakes in Competitive Programming and How to Avoid Them One thing is for sure. You do make mistakes. I also make miskates and that's what makes us human. But what we can surely do is — to try to minimize the errors that we make throughout our life.
I have compiled some of the mistakes that I made in my early Competitive Programming phase. I also mentioned how to avoid them. Also, in most cases, I will give you a chance to find out what the bug is before I reveal the culprit as I tried to make this blog interactive. The codes that I have used in this blog have been written in C++ as it is the most used language for CP.
**So, if you are new to CP, stick with me as you might don't wanna repeat the mistakes that I made when I was a beginner.**
#### Mistake 1
Check out the following code:
<spoiler summary="Code">
~~~~~
#include<bits/stdc++.h>
using namespace std;
int main() {
int a = 1000'000'000,b = 1000'000'000;
long long product = a * b;
cout << product << '\n';
return 0;
}
~~~~~
</spoiler>
The outp...
[Tutorial] Common Mistakes in Competitive Programming and How to Avoid Them, . I have compiled some of the mistakes that I made in my early Competitive
Programming phase. I
100.
Codeforces: acm.sgu.ru comes back <img src="/predownloaded/e6/11/e6110c2bbfaa42c460f7c54f681a89fa9fe2395a.png" alt="acmsguru" title="acmsguru" style="float:right; margin: 0 1em 1em 1em;"/>
Hello everyone!
[acm.sgu.ru](http://acm.sgu.ru/) was created ~16 years ago by programming contests participants from Saratov university: [user:MikeMirzayanov,2018-04-23] and [user:andrewlazarev,2018-04-23]. Today its codebase and infrastructure are completely outdated, and supporting it is unreasonably hard. Nonetheless, Codeforces team is regularly asked to revive acmsguru, since there is still a lot of interest in the problemset.
Here is the new functionality in Codeforces — additional section ["acmsguru" in Problemset](/problemsets/acmsguru). All the problems from the old system are moved there. There are still a few things to do here: correctly port interactive problems, improve looks of statements, support the new section in [Codeforces API](/api/help), support adding these problems to mashups.
Anyway, you can ...
[acm.sgu.ru](http://acm.sgu.ru/) was created ~16 years ago by programming
contests participants
101.
This is not an exit. 
I am looking at the post called [*Is Mike Mirzayanov dictator?*](https://codeforces.me/blog/entry/94033) at the moment. I'm reading through the comments, I'm looking at people's reactions, I'm reading Mike's replies, and... I am utterly disappointed.
I demand progress.
For context, I do believe Codeforces is the best website for competitive programming contests at the moment. I sincerely give credit to Mike for creating Codeforces and providing participants and contest authors a platform for interaction completely for free. I am confident that Codeforces is the most appropriate website for being *the* platform for sharing knowledge, exchanging tricks and methods, and collaboration between both contest participants, their authors, and coordinators.
**Please consider this an open letter**, for this is a will not of a single person, but of many individuals. Please consider signing it by stating so in a comment under the...
For context, I do believe Codeforces is the best website for competitive
programming contests at
102.
Ten years of Competitive Programming Hey Codeforces!
I’m AmirReza PourAkhavan, Codeforces Contest Coordinator. I let the story become complete and I’m sharing it now.
The story is about a 16-year competitive programmer, who left his family and migrated to another city alone to follow competitive programming. After seven years, he advanced to the International Collegiate Programming Contest World Finals, twice.
### Why I’m writing this
Six years ago someone asked me [here](https://codeforces.me/blog/entry/45186?#comment-297837) to write my story. I think it can help you to never give up.
### A brief about me
I've been doing competitive programming for ten years. I advanced to ICPC (International Collegiate Programming Contests) World Finals twice, in 2019 at Porto and 2020 at Moscow. At ICPC World Finals 2020, our team took high-honored place twenty-four, which is equal to the top 0.03% of 200k students participating in ICPC.
<center>
<br>
<img width="50%" src="/predownloaded/c2/0c/c20c501bba688...
Ten years of Competitive Programming, Collegiate Programming Contest World Finals, twice., , he advanced to the International Collegiate Programming Contest World Finals,
twice. ### Why I’m, I've been doing competitive programming for ten years. I advanced to ICPC
(International Collegiate, In the 8th grade, we made a team and competed in the HelliNet Programming
Contest which is the most, Programming Contest (super regional competition for ~70 countries) 2021, 2022,
and European Girls Olympiad
103.
A look at Competitive Programming post-hibernation Hello friends!
As I've recollected in a previous [post](https://codeforces.me/blog/entry/97566), I am an old competitor who hadn't really participated since ~2014, and recently got a bout of nostalgia to return to Competitive Programming. So, I did a couple Topcoder SRMs, suffered through some SNWS rounds, participated in [three regional 5hr competitions](https://contest.yandex.ru/3QF2021) on three consecutive days, and dozed off at every Codeforces contest I tried to wake up for.
A lot of things are still the same as 8 years ago: [user:tourist,2022-01-26] is still at the top, grey coders still ask for how many minutes to solve a problem before reading the editorial, Russian university teams [continue winning](https://icpc.global/worldfinals/results) ACM ICPC, and Snarknews never gives up on his alternate competition formats. But in this post, I want to focus on the new patterns that emerged since my last time around.
#### #1: Codeforces rounds timing
Did you know that t...
A look at Competitive Programming post-hibernation, Competitive Programming. So, I did a couple Topcoder SRMs, suffered through
some SNWS rounds, lot of programming contest problems request to find some value modulo a large
prime. The most common, #### #4: The new MOD to rule them all A lot of programming contest problems
request to find some, #### #5: Probabilities modulo MOD One of my favorite topics in programming
contests was always
104.
Codeforces Round #426 announcement _Hello, fellow programming contest enthusiasts!_
We are pleased to invite you to take part in the forthcoming Codeforces Round #426, which is going to be held [at Sunday, 17:35 MSK](https://www.timeanddate.com/worldclock/fixedtime.html?msg=Codeforces+Round+%23426+%28Div.+1+%2B+Div.+2%29&iso=20170730T1735&p1=166&ah=2). In case one of the things you fear most is a Codeforces round being authored by a purple guy, we've got some <s>bad</s>good news for you: this round will feature two CMs – me ([user:x3n,2017-07-28]) and [user:GreenGrape,2017-07-28] – as its writers!
The classic Codeforces rules will be applied to this round. There will be five problems for each division, with three of them shared by both. The round will last for two hours. Forgoing a long-standing Codeforces tradition, we will not have the scoring disclosed until shortly before the contest.
In this round, you are going to assist Slastyona the Sweetmaid – a renowned lover of sweets, cupcakes, can...
_Hello, fellow programming contest enthusiasts!_
Announcement of Codeforces Round 426 (Div. 1)
Announcement of Codeforces Round 426 (Div. 2)
105.
Codeforces Round #905 (Div. 1, Div. 2, Div. 3) Hello, Codeforces!
We are happy to invite you to our experimental round for three divisions, which will take place at [contest_time:1887]. <b>Please note the non-standard start time for the round</b>. Each division will have 5-7 tasks. The round will be held according to the Codeforces rules and will be rated for all three divisions. A few changes regarding the ratings of participants in this competition:
<ul style="list-style-type:square">
<li>In Div.3 the rating of participants is less than 1600. </li>
<li>In the Div.2 ranking, participants range from 1600 to 2099. </li>
<li>In Div.1 the rating of participants is no less than 2100.</li>
<li><b>Please note</b> that after [contest:1884] the rating will not be recalculated until the end of this competition. </li>
</ul>
Let us note that two team Olympiads will be held in parallel on this day and the rounds are based on their tasks:
<ul style="list-style-type:square">
<li> XXI Moscow Team Olympiad, high school stud...
elimination contest for All-Russian Team Olympiad.
* III Open Team Olympiad UMSh in programming
Announcement of Codeforces Round 905 (Div. 3)
Announcement of Codeforces Round 905 (Div. 1)
Announcement of Codeforces Round 905 (Div. 2)
106.
Duality in linear programming. Part 1 — definition and construction Hi everyone!
Previously I [wrote](https://codeforces.me/blog/entry/98334) about theoretical grounds of "aliens trick". Specifically, I introduced the concept of the Lagrangian duality and explained its connection with the trick. Today I want to elaborate a bit more on the concept of dual problems and their applications to linear programming as well as to common problems in competitive programming.
I initially wanted to also write about some applications in competitive programming problems, but given that the introduction is already quite lengthy, I decided to leave it for another blog, while using most common and well-known theoretical examples here, focusing more on how to construct and interpret dual problems to begin with, rather than how to use it in contests.
I think, it is a crucial first step towards using the duality in actual programming challenges.
#### Prerequisites
It is highly recommended to have some general understanding of basic mathematical optimization...
Duality in linear programming. Part 1 — definition and construction, I initially wanted to also write about some applications in competitive
programming problems, but
107.
First time becoming red In yesterday's contest [contest:1815] I've got the achievement which I could not imagine just half a year ago — reach 2400 rating and become GM.
The first time I learned about CF was on 2022.2, that time I registered this account and took my first contest. But my first submission [submission:146390589] on contest got TLE, and I solved 0 problem in this contest. (At that time I didn't know that's because the efficiency of `java.util.Scanner` is extremely low) And because I needed to deal with graduation thesis, I didn't use CF until the end of last year, when I restarted CF contest.
At 4th and 5th contests I solved div2D problems to reach blue. In my 9th contest, I first time solved div2E problem in contest, and I became purple in my 12th contest. In my 14th and 15th contest, I solved div2E problems twice and became orange. In the next weeks, I started to hit the upper limit of my skill, and dropped from orange twice.
In order to improve my skill of competive programming...
me, it's an important meaningful moment in my life of competitive programming.
Hope that I will be, In order to improve my skill of competive programming, I practiced problems in
CF problemset, In yesterday's contest [contest:1815] I've got the achievement which I could
not imagine just half
108.
Dynamic Programming Optimizations Several recent problems on Codeforces concerned dynamic programming optimization techniques.
The following table summarizes methods known to me.
<table>
<tr>
<th>Name</th>
<th>Original Recurrence</th>
<th>Sufficient Condition of Applicability</th>
<th>Original Complexity</th>
<th>Optimized Complexity</th>
<th>Links</th>
</tr>
<tr>
<td><small>Convex Hull Optimization1</small></td>
<td nowrap><small>$dp[i] = min_{j<i}\{dp[j]+b[j] \star a[i]\}$</small></td>
<td nowrap>$b[j] \geq b[j+1]$<br/><small><s>optionally</s> $a[i] \leq a[i+1]$</small></td>
<td nowrap>$O(n^2)$</td>
<td nowrap>$O(n)$</td>
<td nowrap><small>[1](https://web.archive.org/web/20181030143808/http://wcipeg.com/wiki/Convex_hull_trick) [2](https://cp-algorithms.com/geometry/convex_hull_trick.html) [3](https://codeforces.me/blog/entry/63823)<br/>[p1](/contest/319/problem/C)</small></td>
</tr>
<tr>
<td><small>Convex Hull Optimization2</small></td>
<td nowrap><small>$dp[i][j] = min_{k<j}{dp[i-1][k]+b...
Dynamic Programming Optimizations, Several recent problems on Codeforces concerned dynamic programming
optimization techniques. The
109.
OCPC 2026 Winter Hi everyone!
<center><a href="https://ocpc.camp"><img src="https://ocpc.camp/images/ocpc_light.svg" height="80px"></a>
<a href="https://icpc.foundation/"><img src="/predownloaded/43/08/43086529a28ccb5c9f2f2eec560ffa85e09c6881.svg" height="80px"></a></center>
<center>
<b>Supported by</b><br>
<a href="https://www.janestreet.com/join-jane-street/open-roles/?type=students-and-new-grads&location=london">
<img src="/predownloaded/ee/f2/eef26616a3661c658d1545f18ed21fabb14d5871.svg" height="40px" style="margin: 10px 10px 10px 10px;"></a>
<a href="https://www.hudsonrivertrading.com/">
<img src="https://ocpc.camp/images/HRT.svg" height="40px" style="margin: 10px 10px 10px 10px;"></a>
<a href="https://www.silares.com/">
<img src="https://ocpc.camp/images/silares-red.svg" height="40px" style="margin: 10px 10px 10px 10px;"></a>
<a href="https://pinely.com/">
<img src="/predownloaded/0a/0f/0a0f3f67435d1f6e467bc7203d4a2090ba8f92cc.svg" height="40px" style="margin: 10px 10px 10px 10px...
The camp is inspired by various competitive programming camps that we attended
during our active
110.
[Tutorial] A Way to Practice Competitive Programming : From rating 1000 to 2000 Dear Codeforces Community.<br />
<br />
Today I want to share some ways to practice competitive programming and getting rating. I think this is helpful for those who is practicing competitive programming hardly but rating is sluggish. (By the way, on July 17th, I have a project of competitive programming said CombNaf in Japan. I did a lecture about this. Great thanks to the CombNaf's organizer is [user:Nafmo2,2017-07-17].)<br />
<br />
I will write this by **4 steps**: rating **<font color="grey">1000</font> --> <font color="green">1250</font>**, **<font color="green">1250</font> --> <font color="aqua">1500</font>**, **<font color="aqua">1500</font> --> <font color="blue">1750</font>**, **<font color="blue">1750</font> --> <font color="purple">2000</font>**, in Codeforces Rating System.<br />
<br />
Before writing about each step, I wrote it as premise: You don't have to do this way. This is just a way to practice. Ways to practice is different among people, so I think this may n...
[Tutorial] A Way to Practice Competitive Programming : From rating 1000 to 2000, about the types of programming contest.
111.
ETH Zurich Competitive Programming Contest, Spring 2024 in gym Hi everyone!
We organized an onsite [competitive programming contest](https://vis.ethz.ch/en/events/725/) at ETH Zürich on May 11th, 2024. The contest is now uploaded to the Codeforces gym at [contest:105167].
The onsite contest was 5h long and we recommend for you to participate in teams. In the onsite contest only one computer was allowed but participants could access the internet freely. The difficulty of the problemset is slightly easier than a regional ICPC contest but also offers a few hard problems. Difficulty range is from div2 A to div2 G.
Thanks a lot to all problem setters: [user:BenniKartefla,2024-05-16], [user:Lakii,2024-05-16], [user:Lebossle,2024-05-16], [user:MihneaDAVID,2024-05-16], [user:OhLee,2024-05-16], [user:TecTrixer,2024-05-16], [user:ackj,2024-05-16], [user:adamant,2024-05-16], [user:alagorithmet,2024-05-16] and [user:mango_lassi,2024-05-16].
Additionally, a big thanks to all our testers and reviewers: [user:Petr,2024-05-16], [user:Evirir,2024-05-16...
ETH Zurich Competitive Programming Contest, Spring 2024 in gym, Hi everyone! We organized an onsite [competitive programming contest
](https://vis.ethz.ch/en, We organized an onsite [competitive programming contest
](https://vis.ethz.ch/en/events/725/) at ETH
Announcement of ETH Zurich Competitive Programming Contest Spring 2024
112.
I Wrote a Book — For Those Who Truly Want to Grow Hey everyone! I’m excited to share something important with you.
Over the past two years, I’ve walked a long road in competitive programming — through thousands of problems, hundreds of contests, ups and downs, burnout, and bouncing back. And now, I’ve written a book that captures all of that experience.
But this isn’t just a guide. It’s a motivational and educational book — for high school students, university students, and anyone who wants to grow stronger in olympiad programming. Inside, you’ll find:
the raw truth about burnout and how to deal with it,
real strategies for consistent growth,
a personal story — from the very first steps to winning gold,
and most importantly, ideas that will help you reach the top — and stay there.
This book is for everyone: beginners and advanced alike.
Download the PDF:
https://drive.google.com/drive/folders/1NJ5Qx5ci7GrQeMKZhDakVHqaqg1CdNEg
I’ll be truly grateful if you read it and share your thoughts. This isn’t a textbo...
walked a long road in competitive programming — through thousands of problems,
hundreds of contests, Over the past two years, I’ve walked a long road in competitive programming —
through thousands of
113.
Why problem writers should stop saying “It is guaranteed that” Please Stop Guaranteeing Things
==================
There are two common meanings for something being “guaranteed”, and often it is up to the reader to guess the author’s intended meaning. This is annoying and creates unnecessary barriers to entry.
**Meaning #1:** The thing we are guaranteeing is provably true for the given input. The thing we are guaranteeing is simply true. We don’t want to provide a proof since it would be long, unnecessary, and annoying to read, and might spoil the solution, but you have our word that an answer always exists.
Example: We give you two positive integers A and B (1 <= A, B <= 100). Find some positive integer C (1 <= C <= 200) such that C < A + B. **It is guaranteed that some C exists.**
**Meaning #2:** The only input that is legal is input for which this is true. The thing we are guaranteeing might not always be true without this guarantee. Thankfully, we are providing this guarantee so that you only need to concern yourself with solving t...
always possible is usually a nice head start on the problem too. [2019 China
CollegiateProgramming
114.
Hello 2025 by T-Generation Hello to all fans of competitive programming and Codeforces enjoyers! We're happy to invite you to participate in [contest:2057], which will take place on [contest_time:2057].
We, [user:teraqqq,2025-01-03], [user:dope,2025-01-03], and [user:induk_v_tsiane,2025-01-03], have prepared **8 problems** for you, and you’ll have **2 hours and 30 minutes** to solve them. One of the problems is divided into 2 subtasks. The round will be **rated** for all participants.
Huge thanks to [user:MikeMirzayanov,2025-01-03], [user:geranazavr555,2025-01-03], and [user:KAN,2025-01-03] for great systems Polygon and Codeforces!
Special thanks also go to:
- [user:FairyWinx,2025-01-03] for coordinating this round, finding testers, and providing moral and technical support.
- [user:turmax,2025-01-03], [user:LeoPro,2025-01-03], [user:Kapt,2025-01-03], [user:sevlll777,2025-01-03], [user:Pechalka,2025-01-03], [user:Adam_GS,2025-01-03], [user:evjeny_23,2025-01-03], [user:Iura_Shch,2025-01-03], [user...
Hello to all fans of competitive programming and Codeforces enjoyers! We're
happy to invite you to
Announcement of Hello 2025
115.
The Toxic Mindset in Competitive Programming and How to Fight It #### Introduction
Rating is a great measure of skill and a nice way to observe progress by comparing yourself to your past self and seeing where you stand in the community. As great measure as it is, there are a lot of problems that come with it. They have nothing to do with how the rating system works but rather with how human beings function. In this blog post, I will talk about some of the most pressing personal problems that come up with rating and try to provide some advice on how to solve them, speaking from personal experience and from the experience of a lot of other people I know.
#### Associating self-worth to rating
This is, in my opinion, the most significant problem people face, and it also pretty much contains all the following problems as a subset. It's extremely easy to fall into this rabbit hole since, as a competitive programmer, it only feels natural to associate our rating with intelligence and, respectively, our intelligence with self-worth. Why is this su...
The Toxic Mindset in Competitive Programming and How to Fight It, compared to what their last performance was in a contest?, have only learned more by failing in a contest, so I really could have only
improved since then. And, in your abilities after performing poorly in a contest. I also have several
times stopped believing, participated in a contest, and that's what you enjoy, isn’t it? It won't
always go your way, and you, will come on its own, and even if you lose it, it will be easier to gain it
back in the nextcontest., contest? - Get to know new people that don't even do competitive programming.
What's the first
116.
Ten years of competitive programming 3 Hey Codeforces!
I’m AmirReza PourAkhavan, the former Codeforces Contest Coordinator. I let the story become complete and I’m sharing it now.
The story is about a 16-year competitive programmer, who left his family and migrated to another city alone to follow competitive programming. After seven years, he advanced to the International Collegiate Programming Contest World Finals, twice.
Read the previous post [here](https://codeforces.me/blog/entry/108838).
**Read the Persian version** [**here**](https://docs.google.com/document/d/e/2PACX-1vSUoFC9tLgDCji6rSCYy-RYoUG1_6uOQnHz_LlLKe6KksWBYWO4r6clDly5YxIgzu1g3Tj31weDxgWz/pub).
What happened previously
===
I was a lone programmer, in a small city, trying to learn CP and prepare for the Iran national olympiad. It was not as successful as I expected. I tried to change my school and I migrated to Tehran, alone. I entered AE high school to learn from its inspiring teachers.
11th grade
===
First day of school. I got to ...
Ten years of competitive programming 3, Collegiate Programming Contest World Finals, twice.
117.
CerealCodes Summer 2023 Programming Contest <center> Hello Codeforcers :3 </center>
=================
**UPD 1: Opening ceremony on [Friday 7PM EST](https://www.timeanddate.com/worldclock/fixedtime.html?iso=20230811T190000&p1=179). Join our [Discord server](https://discord.gg/qve3dBA8Ek) for more information**
**UPD 2: Contest has started! You may start your window anytime over the next 2 days. Join our [Discord server](https://discord.gg/qve3dBA8Ek) to ask clarifications for any problems. Good luck!**
From the authors behind [contest:1852] and [contest:1853], CerealCodes is excited to announce our Summer 2023 Programming Contest!
This contest will be held on August $13 - 15$ th with a customizable time-frame window. The time limit for novice
is $3$ hours while intermediate and advanced are allowed $3.5$ hours. All of the contest information, including exact start and end times, can be found [here](https://www.cerealcodes.org/contestinfo).
The competition has three divisions: Novice (USACO Bronze-Silver or Div....
CerealCodes Summer 2023 Programming Contest, Summer 2023 Programming Contest!
118.
The D programming language in competitive programming Hi all!
This post is inspired by a question
[here](/blog/entry/51923?#comment-446901) which asks
[user:yosupo,2018-07-28] how using the D progamming language compares to using C++.
I regularly use D where possible in contests (and problemsetting) since 2014,
with some success (for example, a program in D brought me victory in
[AZsPCs: Alphabet City](http://azspcs.com/Contest/AlphabetCity/Standings)).
So I'd like to share my experience.
I'll try to focus on stuff which is important in competitive programming.
The general feeling is as follows.
You can write in D as in plain C when you need full control.
You can also write more like in Python using the powerful standard library.
However, D is a compiled language, so in both cases,
the performance is similar to C++.
Additionally, when the program is written, it is much easier to debug
than a similar program in C++.
For an example, let us look at two solutions of a
[recent problem](/contest/1010/problem/A).
[cut]
...
The D programming language in competitive programming, possible in contests (and problemsetting) since 2014, with some success (for
example, aprogram in, * Compiler bugs. Back in 2014, participating in a 5-hour contest, on average,
meant I have to
119.
2nd Universal Cup. Stage 6: Warsaw Hello Codeforces! I wanted to invite you to participate in the 6th Stage of the 2nd Universal Cup, which will be held from October 21st to 22nd.
The contest is made of problems from the finals of Potyczki Algorytmiczne (a.k.a. Algorithmic Engagements) from the last couple of years, which is the biggest open polish programming competition. There will be two such contests held as Universal Cup stages and in the upcoming weekend you'll be able to face the first of them.
If you participated in any of the PA2020, PA2021, PA2022 or PA special edition **finals**, or happen to know the problems, please don't compete in this contest.
Problems used in the upcoming contest are authored by me and [user:mnbvmar,2023-10-16]. Also a huge round of applause for [user:kostka,2023-10-16], who helped a lot in organization of each edition of PA, coordinated this contest and translated all the statements!
You can participate in the contest in the following time windows:
- 02:00 (UTC) on S...
, which will be held from October 21st to 22nd. The contest is made of problems
from the finals of, The contest is made of problems from the finals of Potyczki Algorytmiczne
(a.k.a. Algorithmic
120.
Problem Topics Good Day to you!
I've been asked to make some topic-wise list of problems I've solved. Even though I couldn't involve all problems, I've tried to involve at least "few" problems at each topic I thought up (I'm sorry if I forgot about something "easy"). I've alredy made such list once anyway I've tried to include more problems now — so here it is:
<spoiler summary="aho">
http://www.spoj.com/problems/ADAJOBS/
URI 2226 (5) //[NICE][NUMBERS][DP]
http://www.spoj.com/problems/SUB_PROB/en/
http://codeforces.me/contest/696/problem/D 8
http://www.spoj.com/problems/AHOCUR/ 5 //Aho-Corassic + DP
https://www.codechef.com/problems/LYRC (5) //Sample aho-brute-force
http://codeforces.me/problemset/problem/346/B //Proposed by [user:bradyawn,2019-08-03]
</spoiler>
<spoiler summary="automat">
6861 [LA] //CYK
UVA 10679 //Suffix Automat
http://www.spoj.com/problems/STRMATCH/ //Suffix Automat — trie might do too
http://www.spoj.com/problems/NSUBST...
Gym 100625D [2013 Benelux Algorithm Programming Contest (BAPC 13)], Gym 100753A [2015 German Collegiate Programming Contest (GCPC 15) + POI 10-T3], Gym 100753K [2015 German Collegiate Programming Contest (GCPC 15) + POI 10-T3], Gym 100818E [2015-2016 ACM-ICPC Southeastern European Regional Programming
Contest (SEERC 2015)], Gym 101020H [2015 Syrian Private Universities Collegiate Programming Contest] N!, Gym 101174K [2016-2017 ACM-ICPC Southwestern European Regional Programming
Contest (SWERC 2016)], Gym 101466E [2017 ACM-ICPC, Universidad Nacional de Colombia Programming Contest
][NICE], http://codeforces.me/contest/834/problem/D (5) //+Dynamic Programming | NICE
121.
New on Codeforces: Allowed Programming Languages Customization for Mashups/Private Trainings Hello!
Codeforces supports a wide range of languages. Just yesterday I supported Java 11.
On the other hand, my website is not only just open public rounds and trainings, but also an advanced system of groups, custom domains and mashups. This ecosystem makes it possible to conduct private trainings, local contests/olympiads, provides the work of computer science clubs, and so on.
Sometimes you ask me to somehow limit the languages that can be used in a particular contest. For example, an official competition is held that does not support Rust. Or this contest is a practical session specifically for classes in Python.
Now you can configure allowed programming languages (more precisely, their groups) for your mashups and private trainings. Thanks for the help to [user:geranazavr555,2019-10-22] who helped to realize this opportunity!
Here are some screenshots of how it looks in action.
<center>
<img src="/predownloaded/49/19/4919e2326a4b99b50aee02f92487a4bb99dbd1f7.png"...
New on Codeforces: Allowed Programming Languages Customization for
Mashups/Private Trainings, . Sometimes you ask me to somehow limit the languages that can be used in a
particularcontest. For example, :300px"/>
You can choose program languages groups your contest supports.
122.
LI2 Contests Announcement — Free Programming Course Hi everyone!
I'm thrilled to invite you to the **LI2 Contest — free collection of high-quality contests to master every topic** — here, on Codeforces! [Group Link! Click here!](https://codeforces.me/group/jtU6D2hVEi/blog)
### Current avialibale list of topics:
Loops; Prefix Sums; Sortings; Binary Search; Recursion; Sweepline; Two Pointers; Linear Data Structers (stack, queue, etc); Graphs, DFS, BFS; Dynamic Programming; DSU; Shortest Paths; Minimum Spanning Tree; Greedy; ...
### Why this course?
I believe that finding high-quality problems is the hardest part of practice, especially when you are only getting your feet wet with competitive programming.
There are many lectures and articles, but not so many open collections of problems for each topic.
### Time-tested
I guarantee you that this course is time-tested, **I used it myself**.
LI2 is short for Boarding Lyceum №2 in Kazan — the school I study in. So we've been using this course for...
LI2 Contests Announcement — Free Programming Course, Structers (stack, queue, etc); Graphs, DFS, BFS; Dynamic Programming; DSU;
Shortest Paths; Minimum, are only getting your feet wet with competitive programming., ### Announcement and Discussion For Each Contest, ### How To Practise Competitive Programming — The Russian Way, Hi everyone! I'm thrilled to invite you to the **LI2 Contest — free collection
of high, I'm thrilled to invite you to the **LI2 Contest — free collection of
high-quality contests to, There are two main "How To Practise Competitive Programming" blogs that I
really love: [Radewoosh's
123.
Codeforces Round 1012 (Div.1, Div. 2, based on THUPC 2025 — Finals) There will, and there shall be a THU round!
===========================================
Nihao Codeforces! After the unfortunate event which led to [contest:2081] and [contest:2082] being unrated last week, we’re back and stronger than ever!
Tsinghua University’s Student Association of Algorithmic Competitions (THUSAAC) is pleased to invite you to participate in [contest:2089] and [contest:2090] on [contest_time:2090]. This round will be RATED for everyone. You will be given 2 hours and 30 minutes to solve 5 problems for division 1 and 6 problems for division 2, and two of each will have subtasks. **Note the unusual time of the round.**
Our team of amazing problem setters include: [user:Iam1789,2025-03-20], [user:Ecrade_,2025-03-20], [user:E.Space,2025-03-20], [user:QuietBeautifulThoughts,2025-03-20], [user:gyh20,2025-03-20], [user:spiritualkhorosho,2025-03-20], [user:dapingguo8,2025-03-20], [user:myee,2025-03-20], [user:abruce,2025-03-20], [user:_lucien,2025-03-20]. Some of ...
Competitions. It is the largest student-run competitive programming contest in
China with the top 100
Announcement of Codeforces Round 1012 (Div. 1)
Announcement of Codeforces Round 1012 (Div. 2)
124.
Bay Area Programming Contest 2025 The Bay Area Programming Contest ([link to last year's announcement](https://codeforces.me/blog/entry/125855)) returns on Sunday, March 2, 2025. Detailed information, which will be updated as the contest day draws nearer, is at [bapc.gunncpc.com](https://bapc.gunncpc.com/). You can register for the contest at [this link](https://forms.gle/4M78YHAnCZENkXwJ8).
The authors for this contest are [user:BucketPotato,2025-02-06], [user:ezraft,2025-02-06], [user:GusterGoose27,2025-02-06], [user:hihitherethere,2025-02-06], [user:lazulib2,2025-02-06], [user:Westin_sheep,2025-02-06]. Thanks to our testers: [user:AlperenT,2025-02-10], [user:Amazed,2025-02-06], [user:amsraman,2025-02-06], [user:andrewxu,2025-02-11], [user:Benq,2025-02-15], [user:canine,2025-02-11], [user:eggag32,2025-02-06], [user:Extile,2025-02-10], [user:izhang,2025-02-10], [user:Jasonwei08,2025-02-06], [user:lethan3,2025-02-06], [user:mwen,2025-02-06], [user:PurpleCrayon,2025-02-07] (more to be added soon!). You can thank (or...
Bay Area Programming Contest 2025, )-- in particular, participants may only look up basic information about their
programming language, The Bay Area Programming Contest ([link to last year's
announcement](https://codeforces.me/blog
125.
Cooperation between Universal Cup and Huawei In the interest of contributing to the community and bridging the gap between competitive programming and industry, we are happy to announce that in the future, Universal Cup will be cooperating with Huawei in many areas.
Huawei will support Universal Cup in future seasons. In the meantime, we will explore the cutting-edge challenges from the industry together as an additional activity during the Universal Cup season. These events might also serve as parts of other official programming competitions. Moreover, we intend to run some interviews and other events together, providing opportunities for communication between participants and the industry. We also hope that in the future, we can invite the top competitive programming teams to compete in the Universal Cup Onsite Final. It will definitely be one of the best events ever! Please stay tuned and support Universal Cup!
### About Universal Cup
The Universal Cup is a non-profit organization dedicated to offering training resour...
training resources for competitive programming teams. Up to now, there are
more than 2600 teams from all, programming and industry, we are happy to announce that in the future,
Universal Cup will be cooperating with
126.
ACPC committee (The Greatest thieves to ever exist in the competitive programming world) **1500 USD**, contrary to what you may think this is not the price of an NBA finals ticket, it's the registration fees for ACPC (Arab Collegiate Programming Contest), no flight tickets included with mediocre accommodation.
These fees, However, included long opening and closing ceremonies in both of which we had to endure Mohammad Fouad's very dull and lame jokes (one of his childish doings: he stopped the opening ceremony, made us all stand then laughed and told us to sit down...).
Being funny was definitely not their strongest suit. Nor was organization for that matter, atrocious organization with hours spent exposed to extreme Egypt weather.
In addition to all of this, we had to starve our way through the competition with the very cheap and inedible food they provided.
**The most suspicious part was that they only accepted cash payments in dollars (they refused bank transfers or any other traceable payment methods) only dollars and only in CASH !!!!!!!**
You are pro...
ACPC committee (The Greatest thieves to ever exist in the competitive
programming world), comment here for more details](https://www.quora.com/The-Arab-Collegiate-
Programming-Contest, the registration fees for ACPC (Arab Collegiate Programming Contest), no
flight tickets included with, Second, no one asked for luxury. We are all competitive programming enthusiasts
and participate for
127.
Contest 2050 and Codeforces Round #718 (Div.1 + Div.2) Hello Codeforces!
[contest:1517] will take place on [contest_time:1517]. It's rated for everyone! The score distribution is **500--1250--1500--1750--2500--3000--3000--4000**. You will have 2 hours and 45 minutes to solve 8 problems.
Contest 2050 is initiated by volunteers of the 2050 Conference. You can find out what is 2050 at the end of this blog.
The contest is prepared by
- [user:Fulisike,2021-04-21], [user:littlelittlehorse,2021-04-21], [user:Retired_MiFaFaOvO,2021-04-21], [user:xyz2606,2021-04-21]
and we'd like to thank
- [user:KAN,2021-04-23], [user:Nebuchadnezzar,2021-04-21] for their excellent coordination.
- [user:absi2011,2021-04-21], [user:chitanda,2021-04-21], [user:Gromah,2021-04-21], [user:Itst,2021-04-21], [user:_cherry_,2021-04-21], [user:Aaeria,2021-04-21], [user:HIS_GRACE,2021-04-21], [user:A.K.E.E.,2021-04-21], [user:namanbansal013,2021-04-21], [user:Miracle03,2021-04-22], [user:yaoR,2021-04-23], [user:sshwyR,2021-04-23], [user:chenjb,2021-04-23]...
Contest 2050 and Codeforces Round #718 (Div.1 + Div.2), Algorithms and programming are their pleasures of life. With the belief of
victory, they defeated, Hello Codeforces! [contest:1517] will take place on [contest_time:1517]. It's
rated for everyone
Announcement of Contest 2050 and Codeforces Round 718 (Div. 1 + Div. 2)
128.
An archive of old USACO Problems As we know, USACO is a competitive programming contest primarily for secondary school students in the US. It offers a large collection of excellent problems, from the easy to the difficult. Many of the problems are educational and worthwhile as training material.
However, the official website only offers problems from as early as 2011, and older problems are hard to find. Some of the Online Judges, such as POJ, contain some of the problems, but they are not properly filed together, and it's difficult to find the corresponding solution and test data.
In this post, I will try to list all the USACO materials that I have found so far. Most of the materials come from some old websites, and thanks to the efforts of web.archive.org, we can check out old websites that no longer exist. In addition, many of the problems were used as training materials in the training of Chinese IOI teams about 20 years ago. These materials have been preserved and are available through some Chinese websit...
As we know, USACO is a competitive programming contest primarily for secondary
school students in
129.
Shallowest Decomposition Tree Hi Codeforces!
Today I want to tell you about a really cool and relatively unknown technique that is reminiscent of Centroid decomposition, but at the same time is also completely different.
The most common and well known decomposition tree algorithm out there is the centroid decomposition algorithm (running in $O(n \log n)$). It is a standard algorithm that is commonly used to solve tons of different kind of divide and conquer problems on trees. However, it turns out that there exists another closely related decomposition tree algorithm, that is in a sense optimal, and can be implemented to run in $O(n)$ time in around $30$ lines of code. I have chosen to call it the _Shallowest Decomposition Tree_. This blog will be all about the shallowest decomposition tree. Something I want to remark on before we start is that I did not invent this. However, very few people know about it. So I decided to make this blog in order to teach people about this super cool and relatively unknown tec...
One final thing I want to mention is that I know of two competitive programming
problems that are
130.
Ten years of competitive programming 2 Hey Codeforces!
I’m AmirReza PourAkhavan, Codeforces Contest Coordinator. I let the story become complete and I’m sharing it now.
The story is about a 16-year competitive programmer, who left his family and migrated to another city alone to follow competitive programming. After seven years, he advanced to the International Collegiate Programming Contest World Finals, twice.
Read the previous post [here](https://codeforces.me/blog/entry/107465).
10th grade
===
Trying alone
------------------
In my tenth grade, the situation got worse. Before that, at least, I had some colleagues and at least a class per two weeks. But in the new grade, these brights disappeared too. Still, I was trying to do it alone. I remember when I learned the Dijkstra shortest-path algorithm and implemented it for the first time, how happy I was.
Suddenly, my rating growth started. As you can see, my rating in Oct ‘14 was 1057 (minimum rating) and In Feb ‘15 I achieved 1761. Those years, >= ...
Ten years of competitive programming 2, Collegiate Programming Contest World Finals, twice.
131.
[Tutorial] Product Trick Hello everyone,<br>
in this tutorial we will see a trick that can be useful in combinatorics and/or DP tasks. In particular, you can use it when the statement says something similar to "the score of an array is the product of its elements, find the sum of the scores over all the possible arrays".
Prerequisites: basic combinatorics and DP
The trick
------------------
The trick is very simple.
"The score of an array $a$ is $\prod_{i=1}^n a_i$" can be rephrased as "if there are $n$ boxes, and the $i$-th box contains $a_i$ distinguishable balls, the score of $a$ is equal to the number of ways to color a ball for each box".
This is quite obvious, but it can be extremely powerful. Let's see some problems that are trivialized by this trick.
[Dwango Programming Contest 6th, problem C](https://atcoder.jp/contests/dwacon6th-prelims/tasks/dwacon6th_prelims_c) (rating: 2618)
------------------
<spoiler summary="Hint 1">
You have to output the sum of the happiness over all po...
[Dwango Programming Contest 6th, problem
C](https://atcoder.jp/contests/dwacon6th-prelims/tasks
132.
Announcement: Microsoft Q# Coding Contest — Summer 2018 Microsoft's Quantum Team has good news for quantum enthusiasts and coders looking for new challenges. We are excited to announce Microsoft Q# Coding Contest — Summer 2018! By entering the contest, you can hone your quantum coding skills by tackling problems of varying difficulty and implementing solutions in the quantum programming language Q#. Winners will receive a Microsoft Quantum T-shirt!
Quantum computing is a radically different computing paradigm compared to classical computing. Indeed, it is so different that some tasks that are believed to be classically intractable (such as factoring integers, computing discrete logarithms on elliptic curves, or simulating physical systems) can be performed efficiently on a quantum computer. Microsoft recently introduced the Quantum Development Kit which includes Q# — a new programming language to express quantum programs in a way that makes it easier for classical coders to enter the space. Q# integrates into [Visual Studi...
Announcement: Microsoft Q# Coding Contest — Summer 2018, challenges. We are excited to announce Microsoft Q# Coding Contest — Summer
2018! By entering the, in the main contest. Participation in the warmup round is entirely optional.
The warmup round gives
133.
MIT Informatics Tournament 2025-26 Winter Contest **UPD 4:** The contest problems and editorials are available in Codeforces gym:
[MITIT Winter 2025-26 Advanced Team Round](https://codeforces.me/gym/106250)
[MITIT Winter 2025-26 Beginner Round](https://codeforces.me/gym/106251)
[MITIT Winter 2025-26 Advanced Individual Round](https://codeforces.me/gym/106249)
**Editorials:** [Team Round Editorials](https://codeforces.me/gym/106250/attachments/download/34709/MITIT_Winter_2025_2026_Team_Editorials-1.pdf).
**UPD 3:** All contests have ended. Thank you all for participating! We will release the rankings and editorials soon.
**UPD 2:** The team contest has officially started. You can view the [live scoreboard](https://mitit.org/Contest/ViewScoreboard/advanced-team-25-26) here.
**UPD 1:** The contest has officially started. Good luck and have fun!
Please join our Discord server [here](https://discord.gg/gmTUzcezv4) for the latest information!
Hello Codeforces!
We ( [user:ETK.,2025-11-06], [user:flame...
MIT Informatics Tournament 2025-26 Winter Contest, **UPD 4:** The contest problems and editorials are available in Codeforces gym:
[MITIT Winter, M(IT)² is a full-day competitive programming event hosted by MIT students, open
to **high school
134.
Rayan 2025 World Finals **👋 Salam, Codeforces!**
------------------
We are excited to announce that the final round of the **Rayan Programming Contest** will be held **onsite in Tehran**, from **November 25–29, 2025**!
All participants ranked **1-1000** in the [Rayan Selection Round](https://codeforces.me/contest/2034/standings) are invited to complete the [registration form](https://rayan.global/registration/) by <s>August 25, 2025</s> **August 27, 2025**. The final list of invited participants—selected based on rank and geographical diversity—will be announced shortly thereafter.
Beyond the chance to win **top-tier prizes worth $40,000 USD**, finalists will enjoy a unique opportunity to experience the timeless beauty and rich heritage of **ancient Persia**, with special highlights from the vibrant city of [Tehran](https://rayan.global/gallery/tehran-attractions/).
<img src="https://rayan.global/files/Golestan-Palace.jpg" style="width: 100%;">
**Hotel accommodation, local transportat...
round of the **Rayan Programming Contest** will be held **onsite in Tehran**,
from **November 25–29
135.
[RANT] Warning to other coordinators about Wuhudsm Hi again, it is me. I want to preface this blog by saying that I am totally aware that it is not good netiquette to screenshot private messages and publish them publicly. But honestly, I can't care anymore now.
Below is an unorganized rant. Sorry, I'm too pissed to write the things below concisely. And here: I'm pinging him: [user:wuhudsm,2024-07-21].
In an ideal world, I could probably just tell him privately to stop doing it. But I already did. So I think I need to write this blog to either stop him from doing this again or just soft-ban him from authoring more rounds by telling everyone about it.
Let me just preface this blog with a fact of coordination -- it is very possible that problems from contest A will be used in contest B even after testers from contest A have seen those problems. So there are indeed (many) testers who could possibly be affected by this. Some examples of this happening (where I was involved):
- Contest problems based on on-site contests were quit...
that problems from contest A will be used in contest B even after testers from
contest A have seen
136.
Unbelieveable story of success at ACM ICPC final Preparing to contest
====================
For long time I haven't been writing stories about my life. As Nietzsche said — Bredor died, and I don't feel
so good myself. You might be thinking that I went into booze.
Actually, I have really been drinking so much all this time, but I had more important activities: once upon a time I came to my college to find a company to drink. There I saw an advertisment about programming competitions, but I found that competitive programming is sense less in school and it didn't attract my attention. Soon, I was summoned to the dean, and the dean told me: "mr. Rudolph Gotov, there is noone except you who can win this contest!". I refused him at first time certainly, but then he offered me hard choices such as to continue winning all contests or to stop to arrange night parties at college campus. The choice was not great, and I went looking for a team. Because of stupid rules I could not invite my friends from Bratsk into the team, so I had t...
programming competitions, but I found that competitive programming is sense
less in school and it
137.
XXII Open Cup: GP of EDG Hello! I'm happy to announce XXII Open Cup: Grand Prix of EDG, which will be held on Nov 14th, 2021.
This contest is mainly prepared by Zhejiang University, which has already been used as the 2021 CCPC Guilin Contest.
On the same day of the 2021 CCPC Guilin Contest, Team [Edward Gaming (EDG)](https://en.wikipedia.org/wiki/Edward_Gaming) from [League of Legends Pro League (LPL, China)](https://en.wikipedia.org/wiki/League_of_Legends_Pro_League) won the Champion of [the 2021 League of Legends World Championship](https://en.wikipedia.org/wiki/2021_League_of_Legends_World_Championship) held in Reykjavík. They are also the only LPL team entering the semi-finals while the rest of three teams all coming from [League of Legends Champions Korea (LCK, Korea)](https://en.wikipedia.org/wiki/League_of_Legends_Champions_Korea), including the champion from last year. Almost nobody would bet on their winning, but they made it and reclaim the glory for LPL after 2 years.
. Of course, the other advantage of asking questions there is that I'll be around to answer them. Additionally, my hope is that having a community with which to train is likely to help people who don't have other competitive programmers around locally find motivation to grow.
2. Helping people create training plans and find helpful resources to use while practicing. While I'm not convinced t...
Introducing Competitive Programming Academy, bouncing around include the aforementioned mentoring program, lectures (with
accompanying problemsets, 1. To provide a programming competition community focused specifically on
training and growth, Hi all! I'm proud to announce **Competitive Programming Academy**, my new
programming
139.
Codeforces: Results of 2020 [Annual Report] Hi Codeforces!
Yes, I know it's already April. Time flies so fast lately! Exactly a year ago we were just learning all the "delights" of lockdown.
So let's remember this 2020! What was it like? I don't know about you, but we had a hell of a lot of work.
I will now show you some graphs and you will be very surprised. Lockdown effect? Of course, but we did our best too.
Many thanks to everyone who did not stand aside! In 2020, we celebrated our 10th anniversary and crowdfunding money helps us grow and move forward. You helped us and each other. Thank you.
<a href="https://codeforces.me/10years/supporters">Thank you for your contribution!</a>
We've been working hard all year to make this community a better place. Did it work out? It's up to you to judge.
Many thanks to everyone who invested time and effort:
* [user:geranazavr555,2021-04-09], [user:kuviman,2021-04-09], [user:cannor147,2021-04-09] helped a lot with development and new features;
* [user:Una_Shem,2021-...
* **JetBrains**, Kotlin Heroes Rounds — Kotlin programming language contests *
**Huawei** &mdash
140.
The 2019 China Collegiate Programming Contest Harbin Site (Online Mirror) in Gym Hello, Codeforces!
The China Collegiate Programming Contest (CCPC) is a competitive programming contest series for college students in China, organized by the CCPC Committee, which consists of coaches of the competitive programming teams of Chinese universities. It started in 2015, and this year is the 5th edition of CCPC. There are 4 onsite CCPC contests this year, including three regional contests in Qinhuangdao, Harbin and Xiamen, as well as the CCPC Final in Beijing. Many Chinese universities use CCPC as an opportunity to practice before the ICPC regionals.
The 2019 CCPC Harbin Site has recently ended on October 13 in Northeast Forestry University. A total of 272 teams, most of whom were selected from the preliminary online contest, took part in the official onsite contest in Harbin. The problems for this contest were mostly prepared by retired ICPC participants of Zhejiang University, and the head judge was me.
We are glad to invite you to participate in its online mirro...
The 2019 China Collegiate Programming Contest Harbin Site (Online Mirror) in Gym, Hello, Codeforces! The China Collegiate Programming Contest (CCPC) is a
competitiveprogramming, The China Collegiate Programming Contest (CCPC) is a competitive programming
contest series for
141.
Judges adding tests against submitted solutions during the contest In the discussion at [http://codeforces.me/blog/entry/6870#comment-125383](http://codeforces.me/blog/entry/6870#comment-125383) it became apparent that [user:Jacob,2013-03-11] has submitted a solution for Round 172 Problem E that passed all system tests, and was not challenged, but in the end he didn't get the score for it because a tester has decided to stress-test it against a correct solution and add tests where it fails to the system test.
I think this is an awful, awful decision, as it goes against the spirit of progamming competitions: automatic judging and complete objectivity it gives.
There are so many ways this can discriminate against [user:Jacob,2013-03-11]:
- Had I submitted a solution for problem E, the tester might not suspect it would be a wrong greedy (because I'm in top 10 by rating) and would not add tests, and I'd get the points.
- Maybe some people who opted for solving problem D instead also submitted wrong solutions, but since there were more than one...
Judges adding tests against submitted solutions during the contest, programming competitions, in my opinion, relies on this one aspect: automatic
judging. Please don't
142.
Ten Years of Competitive Programming 4 Hey, Codeforces!
I’m AmirReza PourAkhavan, the former Codeforces Contest Coordinator. I let the story become complete and I’m sharing it now.
The story is about a 16-year competitive programmer, who left his family and migrated to another city alone to follow competitive programming. After seven years, he advanced to the International Collegiate Programming Contest World Finals, twice.
Read the previous parts: [1](https://codeforces.me/blog/entry/107465), [2](https://codeforces.me/blog/entry/108838), [3](https://codeforces.me/blog/entry/114356).
**Read the Persian version** [**here**](https://docs.google.com/document/d/e/2PACX-1vSUoFC9tLgDCji6rSCYy-RYoUG1_6uOQnHz_LlLKe6KksWBYWO4r6clDly5YxIgzu1g3Tj31weDxgWz/pub).
What happened previously
===
I was a lone programmer, in a small city, trying to learn CP and prepare for the Iran National Olympiad. It was not as successful as I expected. I tried to change my school and I immigrated to Tehran, alone. I entered AE high s...
Ten Years of Competitive Programming 4, Collegiate Programming Contest World Finals, twice.
143.
Bay Area Programming Contest 2024 Hi Codeforces,
Gunn High School's competitive programming club will be hosting the Bay Area Programming Contest on March 3, 2024. You can find our website, with detailed information, at [bapc.gunncpc.com](https://bapc.gunncpc.com/). You can register for the contest at [this link](https://forms.gle/yhwt4j8BoG9vKXMZ8).
Problems were set by [user:ezraft,2024-02-13], [user:GusterGoose27,2024-02-13], [user:lce4113,2024-02-13], and [user:Ench_Lolz,2024-02-13] with help from [user:BucketPotato,2024-02-13] and [user:qpwoeirut,2024-02-13].
Thanks to our testers: [user:willy108,2024-02-13], [user:izhang,2024-02-13], [user:Jasonwei08,2024-02-13], [user:flamestorm,2024-02-13], [user:amsraman,2024-02-13], [user:eggag32,2024-02-13], [user:EnDeRBeaT,2024-02-19], [user:NightWizard777,2024-02-21], [user:Feet_McYeet,2024-02-21] and especially to [user:myst-6,2024-02-13], [user:omeganot,2024-02-14], and [user:Benq,2024-02-21].
## Time and place
The contest will be held **in-person** at G...
Bay Area Programming Contest 2024, Gunn High School's competitive programming club will be hosting the Bay Area
Programming Contest on, Programming Contest on March 3, 2024. You can find our website, with detailed
information, at
144.
Squarepoint Challenge (Codeforces Round 1055, Div. 1 + Div. 2) Annyeonghaseyo, Codeforces!
We invite you to participate in [contest:2152], which will be held on [contest_time:2152].
The round will be **rated for everyone**. You will be given **8 problems**, one of which is divided into two subtasks, and **3 hours** to solve them. One of the problems will be interactive, so make sure to read the [guide for interactive problems](https://codeforces.me/blog/entry/45307) before the contest.
The problems are authored and prepared by [user:as_dfsdf,2025-09-29], [user:djm03178,2025-09-29], [user:ko_osaga,2025-09-29], and [user:qwerasdfzxcl,2025-09-29].
We would like to thank:
- [user:errorgorn,2025-09-29] for great coordination.
- [user:Alexdat2000,2025-09-29] for great Russian translation.
- [user:Adam_GS,2025-09-29], [user:ainta,2025-09-29], [user:bangan,2025-09-29], [user:BuzzyBeez,2025-09-29], [user:cookiedoth,2025-09-29], [user:Dragos,2025-09-29], [user:gamegame,2025-09-29], [user:garam1732,2025-09-29], [user:Geothermal,2025-09-29],...
Annyeonghaseyo, Codeforces! We invite you to participate in [contest:2152],
which will be held
Announcement of Squarepoint Challenge (Codeforces Round 1055, Div. 1 + Div. 2)
145.
Returning to In-Person GCJ/Hacker Cup Finals In the past, most elite programming competitions (e.g. IOI, ICPC, TopCoder Open, AtCoder World Tour, GCJ, Hacker Cup) have held their final stages in person. In 2020 and 2021, however, most of these contests were moved online. This was unfortunate, but understandable given the circumstances: in 2020, the state of the pandemic clearly did not allow for extensive travel, and while the dangers decreased by late 2021 as a result of rising vaccination rates around the world, there was still sufficient uncertainty to justify holding events online in 2021.
This year, however, both Google Code Jam and Meta Hacker Cup have committed to hosting online finals. [**UPD:** Meta has retracted its commitment to a virtual finals, so it seems that the plans for MHC are still up in the air.] I believe that this is a highly unnecessary precaution--there is plenty of evidence showing that it is possible to successfully run an in-person event in 2022. Notably, TopCoder has committed to hosting the...
, including Oculus Quests for all the finalists, and organizing card games
after thecontest). Even, In the past, most elite programming competitions (e.g. IOI, ICPC, TopCoder
Open, AtCoder World Tour
146.
Algorithm Gym :: Graph Algorithms Welcome to the new episode of [user:PrinceOfPersia,2015-01-31] presents: Fun with algorithms ;)
You can find all the definitions here in the book "Introduction to graph theory", Douglas.B West.
[cut]
Important graph algorithms :
DFS
---
The most useful graph algorithms are search algorithms. DFS (Depth First Search) is one of them.
While running DFS, we assign colors to the vertices (initially white). Algorithm itself is really simple :
~~~~~
dfs (v):
color[v] = gray
for u in adj[v]:
if color[u] == white
then dfs(u)
color[v] = black
~~~~~
Black color here is not used, but you can use it sometimes.
Time complexity : $O(n + m)$.
#### DFS tree
DFS tree is a rooted tree that is built like this :
~~~~~
let T be a new tree
dfs (v):
color[v] = gray
for u in adj[v]:
if color[u] == white
then dfs(u) and par[u] = v (in T)
...
programming contests.
147.
ICPC should NOT be done online I have been thinking about this for more than a year. I think it's time to share my thoughts. **Disclaimer: all opinions written in this post are purely personal and not tied with any affiliation/institution I am working with.**
The [global pandemic we are encountering](https://en.wikipedia.org/wiki/COVID-19_pandemic) has affected many aspects of our life. While we need to adapt to doing most of our activities online, competing in the [International Collegiate Programming Contest (ICPC)](https://en.wikipedia.org/wiki/International_Collegiate_Programming_Contest) -- or similar high-stakes team programming contest -- should not be one of them.
I have no objection to the following online contests: International Olympiad in Informatics (IOI), Google Code Jam (GCJ) final, Facebook Hacker Cup (FBHC) final, and any similar contest final which is participated by the best ~20 competitive programmers in the world. What makes them different from ICPC is the amount of trust we have put in th...
, competing in the [International Collegiate Programming Contest
(ICPC)](https://en.wikipedia.org/wiki
148.
I have solved problems on Codeforces for 500 days in a row It's been a while since I started my journey into competitive programming and in this year and (almost) a half I would say that I learned a bit not only about problem solving but also about myself, so I wanted to share my reflections on some mental aspects of practicing competitive programming hoping they can help someone else.
Please note that these reflections are merely personal and mostly stem from personal experience, if you disagree with something I would like to know your point of view!
I would also like to thank [user:Intellegent,2025-12-08], [user:turska,2025-12-08] and [user:LMeyling,2025-12-08] for proofreading.
#### Some background
I used to do math olympiads for 8 years before starting university, in hindsight I did not really like it that much since I never practiced on my own and would've rather played League of Legends / Minecraft / VALORANT or whatever game I was obsessed at the time. ...
#### How I got into competitive programming The first time I heard about
Codeforces was in my
149.
1 on 1 Competitive Programming Coaching Hello Codeforces!
#### Coaching
I am a USACO Platinum contestant, former Codeforces International Master rated 2377, Leetcode 2600, member of the [Binarysearch.com](http://binarysearch.com) contest team, and author of [contest:1548] and [contest:1549]. I'm offering **one on one** competitive programming lessons OR leetcode practice, online over Zoom.
- I can help you get better at [USACO](http://usaco.org).
- I can help you gain Codeforces rating.
- I can help you with [Leetcode.com](http://leetcode.com) and [Binarysearch.com](http://binarysearch.com) problems. I can help explain common interview programming techniques.
#### Price
The price is **$50 an hour** due to exceptionally high demand.
#### Interest
If you're interested, please send a direct message to [user:Agnimandur,2021-08-12] over Codeforces! Alternatively, send a direct message over [Discord](http://discord.com) to **Agnimandur#9256**.
#### Frequently Asked Questions
Suggest more questions in the com...
1 on 1 Competitive Programming Coaching, of [contest:1548] and [contest:1549]. I'm offering **one on one** competitive
programming lessons OR
150.
About the Universal Cup, the Semifinals, and myself... Hey'all!
This gonna be a long post, so let me put an important TLDR here first: we are going to host **The 3rd Universal Cup Semifinals**, which will take place on August 24, 2025 **online**, at [11:00 (UTC)](https://www.timeanddate.com/worldclock/fixedtime.html?msg=The+3rd+Universal+Cup+Semifinals&iso=20250824T19&p1=33&ah=5). This contest will be a part of our Finals Team Selection, which the detailed rules and announcements will be published later next week.
---
Now for some extra context, if you're interested.
Last week, we hosted the [last online stage](https://codeforces.me/blog/entry/143954) of The 3rd Universal Cup. After that, I posted a [feedback form](https://docs.google.com/forms/d/1g5Txhiirh_lRsvGfkYWRozu0WDDGK31IAXjB7VgeVoM/edit) on our discord server. I received lots of thoughtful responses (P.S — it's still open, so feel free to fill it out if you haven't yet!).
I've read through all the feedback, and I'd like to share a few thoughts.
### On the Number...
+Semifinals&iso=20250824T19&p1=33&ah=5). This contest will be a part of our
Finals Team Selection, which the
151.
Codeforces Round #547 (Div. 3) Hello, Codeforces!
I am pleased to invite you to [contest:1141], which will start on [contest_time:1141]. Everyone whose current rating is strictly less than 1600 is invited to participate officially. All others can take part out of the competition.
It so happened that the schedule of this month is not replete with rounds (coordinators, we hope for you!). Therefore I decided to partially correct the situation. All the problems of this round were invented and prepared by me on the last day of [Hello Muscat Programming Bootcamp 2019] (/blog/entry/63298) and on flights from Muscat to St. Petersburg. I even specially noted the time for preparation: for the current moment (the problems are ready for testing) I spent about 6 hours on their preparation, including inventing some of the problems. I really like working on problems, this is something at the intersection of creativity and programming. I really hope you enjoy the result of my work.
<center>
<br/>
<img src = "/predownload...
Hello, Codeforces! I am pleased to invite you to [contest:1141], which will
start on
Announcement of Codeforces Round 547 (Div. 3)
152.
Changes in Codeforces problem style over 2020 Sorry for my poor English.
I am talking only from Div2 perspective as I think Div1 contest are still ok from this point of view.
During 2020 codeforces moved from having problems with variation over known algorithms and data structures to constructive heavy contests. I am not saying that having constructive problems are bad but their amount is way too high and I guess most of us will agree that now a days problems on topics like binary search, DP, Graphs or segment tree or other data structures etc are almost extinct in Div2 rounds.
Lets take last Div2 [contest:1474] as an example someone who knows programming language and basic number theory could solve problems till E and can get 1st rank. So in theory someone could become a master or International Master with just number theory and programming language knowledge.
I used to like constructive problems a lot (Actually one of my stronger topics) but now a days there are just so much constructive problems that they ...
Lets take last Div2 [contest:1474] as an example someone who knows programming
language and basic
153.
Programming contest book reviews There are several programming contest books, but what do they contain and how good are they? Of course, it is difficult to know before buying and reading them. In this blog post I review programming contest books that I have read.
Do you know other books or have different opinions?
***
- **Programming Challenges: The Programming Contest Training Manual**
- URL: [http://www.programming-challenges.com/](http://www.programming-challenges.com/)
- Authors: Steven Skiena & Miguel Revilla
- Year: 2003
- Price (Amazon): 56.67 USD (paperback)
This is a classic book about programming contests, written more than ten years ago.
The book contains 14 chapters that discuss topics such as data structures, combinatorics, dynamic programming, and computational geometry. Each chapter begins with an introduction to the topic, followed by a collection of programming tasks.
A lot has happened in the world of programming conte...
Programming contest book reviews, introduction to programming contests I have read. The authors know what they
are speaking about, and the, the reader already has a strong background in programming contests., - **Competitive Programming 3: The New Lower Bound of Programming Contests** -
URL: [http, - **Programming Challenges: The Programming Contest Training Manual** - URL:
[http, A lot has happened in the world of programming contests during the last ten
years. While many, The book is a good resource for getting a general picture of the topics that
appear inprogramming, There are several programming contest books, but what do they contain and how
good are they? Of, This book contains a collection of tasks from Polish programming contests
organized by the, This is a classic book about programming contests, written more than ten years
ago., programming contests. The book is intended for readers who have some background
in algorithmprogramming. Both
154.
Ten Years of Competitive Programming 5 Hey, Codeforces!
I’m AmirReza PourAkhavan, the former Codeforces Contest Coordinator. I let the story become complete, and I’m sharing it now.
The story is about a 16-year-old competitive programmer who left his family and migrated to another city alone to follow competitive programming. After seven years, he advanced to the International Collegiate Programming Contest World Finals twice.
Read the previous parts: [1](https://codeforces.me/blog/entry/107465), [2](https://codeforces.me/blog/entry/108838), [3](https://codeforces.me/blog/entry/114356), [4](https://codeforces.me/blog/entry/122483).
**Read the Persian version** [**here**](https://docs.google.com/document/d/1TN8pnS_8te7MLDYzMjlDxFrElNVjE4ZWjo1Ak-JJdmc/edit?tab=t.isfroku1gx3e).
This part covers from December 2016 to November 2017.
## The Codeforces Contest
Our contest was held on Codeforces, and it broke several records.
- The record for the highest number of upvotes on an editorial.
- The record f...
Ten Years of Competitive Programming 5, Collegiate Programming Contest World Finals twice.
155.
My winning theory in IOI 2018 & 2019 — Why I won 2 golds in IOI Dear Codeforces community.<br />
According to [IOI 2019 Results](http://stats.ioinformatics.org/results/2019), I got the 25th place and got successful gold medals twice in a row.<br />
Although it was pretty close to the gold-medal border (only 6.14pts / 600 difference) and it was lower performance than IOI 2018, which I participated when I was orange in Codeforces, I had many chances to get more points in this IOI, even for top 10. Since there are not so many people who have got two gold medals in IOI (and there were many requests like "I want [user:E869120,2019-08-14] to talk about how to get gold in IOI" like [this comment](https://codeforces.me/blog/entry/66909?#comment-510127) and [this comment](https://codeforces.me/blog/entry/66909?#comment-513129)). I want to write something about IOI, which may be useful for people who will participate in IOI next year and also some years later.<br />
<br />
<br />
### A. First of all
At...
/source/Tasks/Day1/Split/split.pdf). If you want to gain Codeforces /
competitiveprogramming skills
156.
When Dreams Come True: The only solve on N at ICPC WF 2020. _Addendum: This is mostly about the story behind our solution to N. To see more about the math, see [here](https://codeforces.me/blog/ekzhang)_
When I was younger, fairytales always captivated me, with their nice and clean stories. All through my life I've liked the idea of having a fairytale ending to a life arc, but I was frequently disappointed. Many times after an unsuccessful experience, one simply gets more unsucessful experiences and then time runs out...
At ICPC recently, I was lucky enough to finally attain my fairytale ending to my competitive programming career. I figured I would tell the fairytale, to close a career that started about 6 years ago.
On my World Finals team, my role is to help the team get hard math problems, as I haven't actively processed algorithms in years. So imagine my delight when my teammate ([user:ekzhang,2021-10-06]) points out that problem N reduces to finding a vector so that the (l2)-norm of x is r, and $Ax = b$ for a matrix $A$ and vect...
At the last few programming contests I've participated in, run-time error has
been a pretty common, His program passes the samples, but doesn't pass the large case either. There
are now about $10
157.
[AtCoder] Educational DP Contest <p style='font-size: large; color:red;'>
<strong>The contest was postponed to <a href='https://www.timeanddate.com/worldclock/fixedtime.html?iso=20190106T11&ah=5'>2019-01-06(Sun) 11:00-16:00 UTC</a>.</strong>
</p>
Hello, Codeforces!
We will hold **[Educational DP Contest](https://atcoder.jp/contests/dp)** at AtCoder on Saturday.
#### About the Contest
This is an unofficial contest to practice **DP (Dynamic Programming)**.
We selected 26 DPs, mostly basic ones, and prepared a problem to learn each of them.
Test your skills during the real contest, and brush them up after it ends.
#### Details
- Time (YY-MM-DD): [2019-01-06(Sun) 11:00-16:00 UTC](https://www.timeanddate.com/worldclock/fixedtime.html?iso=20190106T11&ah=5) (<strong>postponed</strong>)
- Duration: 5 hours
- Number of Tasks: 26
- Point Values: 100 points each
- Rated: No
#### Rules
[The rules for ABC, ARC and AGC](https://atcoder.jp/contests/dp/rule) apply.
The important points are:
- This ...
[AtCoder] Educational DP Contest, This is an unofficial contest to practice **DP (Dynamic Programming)**. We
selected 26 DPs, mostly
158.
Competitive Programming Roadmap (target: [gray, blue]) tl;dr
------------------
- Competitive programming roadmap [here](https://drive.google.com/file/d/16Jydn250Ue7K7hOfzLxw4p5jFF4ZCqWT/view?usp=sharing).
- It should be suitable both for newcomers and for people with some experience with CP: let's say, up to blue on Codeforces.
- It contains ~ 100 "must-know" problems about various topics: ad-hoc, STL, binary search, DP, number theory, graphs.
- There are solution sketches at the bottom, don't feel guilty reading them if stuck.
Why?
------------------
Many people new to Codeforces seek advice about how to get better / which problems to try. Other people are stuck on gray / green even after solving a lot of problems. This roadmap aims to be a solution.
My take: to be good at competitive programming, you have to know "what to think" and "how to think" when you try a problem.
- "What to think": you have to know a decent amount of standard problems / techniques. Sometimes, a problem requires steps / observations that seem ob...
Competitive Programming Roadmap (target: [gray, blue]), tl;dr ------------------ - Competitive programming roadmap
[here](https://drive.google.com/file
159.
OCPC 2025 Summer Hi everyone!
<center><a href="https://ocpc.camp"><img src="https://ocpc.camp/images/ocpc_light.svg" height="100px"></a>
<a href="https://icpc.foundation/"><img src="/predownloaded/43/08/43086529a28ccb5c9f2f2eec560ffa85e09c6881.svg" height="100px"></a></center>
<center>
<b>Supported by</b><br>
<a href="https://www.janestreet.com/join-jane-street/open-roles/?type=students-and-new-grads&location=london">
<img src="/predownloaded/ee/f2/eef26616a3661c658d1545f18ed21fabb14d5871.svg" height="60px" style="margin: 10px 10px 10px 10px;"></a>
<a href="https://pinely.com/">
<img src="/predownloaded/0a/0f/0a0f3f67435d1f6e467bc7203d4a2090ba8f92cc.svg" height="60px" style="margin: 10px 10px 10px 10px;"></a>
</center>
... And a happy May day!
We are very happy to announce that OCPC (formerly, the _Osijek Competitive Programming Camp_) is back this Summer, on **June 21-29, 2025**! While the dates are pretty tight, they appear to be the ones that are most suitable (among all the summ...
The camp is inspired by various competitive programming camps that we attended
during our active
160.
Codeforces Round #765. One of the contest authors is entertaining again. Hello, Codeforces! Codeforces #765 (Div. 2) took place not so long ago, and one of its authors was me. When an hour had passed since the contest started, I decided to remember the old days and start making fun of the cheaters.
To that end, I decided to take a look at the old cheater groups and see how they were doing.
The first group I looked into — is the group where the admin is actively fighting against cheaters. So, there really weren't any cheaters on the round. I think that's a success.
The second group I checked out — it's a group with 2.5k users. I decided that just going in there would be too boring, so I decided to write there that I was a contest author. Here's the reaction of the users:
<spoiler summary="Picture">
<a href="https://imgbb.com/"><img src="https://i.ibb.co/0Xt07qt/Screenshot-20220112-164100.png" alt="pic1" border="0"></a>
</spoiler>
Can you imagine?! I write that I am the author of the contest, and I am offered to leak the solution ...
Codeforces Round #765. One of the contest authors is entertaining again., But I stopped communicating when I realized what he was really into sports
programming for.
161.
700 contests. ruban's interview Please meet my today's guest Anatoly [user:ruban,2021-05-17], PhD in Physics and Mathematics, who yesterday participated in his 700th contest on Codeforces.
[cut]
_._
_-Hello Anatoly_
-Hello Natalia
_-Were you surprised by my message that you had taken more contests on Codeforces than anybody else?_
-No, I wasn’t. I knew it for sure. There have been only several occasions when I missed rounds because of high rating, I think, not many than 20-30.
_-Do you feel something special about contests with the round number like 500th, 600th or this one 700th?_
-No, I wouldn't pay any attention if there were no interview.
_-How did you start on Codeforces?_
-Since 2001 (long before Codeforces) I have coached the competitive programming team of [SibSUTIS](https://sibsutis.ru/en/) — Siberian State University of Telecommunications and Information Science and created problems for All...
students. Though you really need knowledge of discrete math for competitive
programming and I am
162.
COMPFEST 15 Preliminary Online Mirror (Unrated, ICPC Rules, Teams Preferred) <img alt="logo" src="/predownloaded/54/ec/54ec8a2a974eb225636db378f5470e039144d49b.png" style="float: right;height: 100.0px;margin: 10.0px;max-width: 100.0%;max-height: 100.0%;">
Hello, **Codeforces**! 😍😍
We are happy to invite you to participate in [COMPFEST 15 Preliminary Online Mirror (Unrated, ICPC Rules, Teams Preferred)](https://codeforces.me/contests/1866) on <a class="contest-time" contestid=1866></a>. COMPFEST is a national **ICPC-style contest** for university students in Indonesia.
The problems are written and prepared by [user:ArvinCiu,2023-08-30], [user:asteriskzie,2023-08-30], [user:CyberSleeper,2023-08-30], [user:Edbert.H,2023-08-30], [user:FreeJinG,2023-08-30], [user:gansixeneh,2023-08-30], [user:KokiCoder,2023-08-30], [user:nandonathaniel,2023-08-30], and [user:Pyqe,2023-08-30].
We would also like to thank:
- [user:KAN,2023-08-30] for helping to host the mirror round;
- [user:AMnu,2023-08-30], ([user:KerakTelor,2023-08-30], [user:Owmic...
IT event in Indonesia and competitive programming contest is one of the
competitions hosted.
163.
The 7th Turing Cup Tournament # 2025 · The 7th Turing Cup Tournament
The Turing Cup is an invitational competition that is organized by one of the most successful informatics competition teams in China, the XinYouDui and partner with X-Camp Academy.
## Timeline
| Event | Time (UTC+8) |
|----------------------|-----------------------------------------|
| Registration Time | May 06, 2025, 06:00 PM — May 25, 2025, 12:29 PM |
| Opening Ceremony | May 25, 2025, 07:50 AM — 08:30 AM |
| Contest Time | May 25, 2025, 08:30 AM — 12:30 PM |
---
## Contest Details
### Staff
- Writers: [user:dXqwq,2025-05-22], [user:Flamire,2025-05-22], [user:myee,2025-05-22], [user:orzdevinwang,2025-05-22], [user:zhaohaikun,2025-05-22]
- Testers: [user:dspt,2025-05-22], [user:emptyhope,2025-05-22], [user:jqdai0815,2025-05-22], [user:Kubic,2025-05-22], [user:le0n,2025-05-22], [user:zhaohiakun,2025-05-22]
### Features
- **High Contest Q...
## Organizers ### XinYouDui XinYouDui is a world-class competitive programming
training
164.
Rutgers Programming Contest Fall 2025 <img src="/predownloaded/fc/ef/fcef5ca1e0134bbfc1cf9613f346cf5e2392b914.png" alt="RUCP Logo" style="float: right;" width="300px"/>
### Hear ye, hear ye!
We are excited to invite you to participate in the open mirror of the [Rutgers Programming Contest Fall 2025](https://rucp-contest.github.io/), which will start [Sunday, November 23, 2025 at 1:00 PM EST (UTC-5)](https://www.timeanddate.com/worldclock/fixedtime.html?msg=Fall+2025+Rutgers+Programming+Contest&iso=20251123T13&p1=5276&ah=5).
The problems were prepared and authored by [user:jdurie,2025-11-16], [user:nickbelov,2025-11-16], [user:nadya271,2025-11-16], and [user:ScalarField,2025-11-16].
The contest is a **5-hour long** ICPC-style team contest consisting of **15 problems**. Team sizes can be anywhere from 1 to 3 people. Teams of more than one person are kindly requested to only use one computer for the contest. At least one of the problems will be interactive, so please read [the guide](https://codeforces.me/blog/e...
Rutgers Programming Contest Fall 2025, We are excited to invite you to participate in the open mirror of the [Rutgers
Programming Contest
Announcement of Rutgers University Programming Contest Fall 2025 - Open Division
165.
Invitation to CodeChef December Lunchtime 2020 We invite you to participate in CodeChef’s [December Lunchtime](http://bit.ly/LTIME91-Codeforces), this **Saturday, 26th December**, from [9:30 pm to 12:30 am IST](https://www.timeanddate.com/worldclock/fixedtime.html?msg=December+2020+Lunchtime&iso=20201226T2130&p1=44&ah=3).
**Note the unusual time.** It starts at 9:30pm instead of the usual 7:30pm
You will be given a total of **8 problems** (6 in Div2, 6 in Div1) to solve in a duration of **3 hours**.
Joining us on the problem setting panel are:
- Setters: Sahil [user:sahi1422,2020-12-25] Chimnani, Venkata [user:Nikhil_Medam,2020-12-25] Nikhil Medam, Áron [user:mraron,2020-12-25] Noszály, Nishant [user:nishant403,2020-12-25] Shah, Yogesh [user:SeismicToss,2020-12-25] Sharma, Hriday [user:the_hyp0cr1t3,2020-12-25], Divyam [user:divyamsingal01,2020-12-25] Singal, Bhavyesh [user:bhvdsi,2020-12-25] Desai
- Tester: Rahul [user:amnesiac_dusk,2020-12-25] Dugar
- Editorialist: Taranpreet [user:taran_1407,2020-12-25] Singh
...
As this is my first contest as CodeChef admin, I wanted to add few words from
myself. Please do
166.
Codeforces Round #492 [Thanks, uDebug!] Hello denizens of Codeforces once again!
After our last [two](http://codeforces.me/blog/entry/21860) [rounds](http://codeforces.me/blog/entry/43848),
Yang Liu ([user:desert97,2018-06-19]) and I ([user:ksun48,2018-06-19]) are pleased to announce Codeforces Round #492, which will happen on [June 24, 2018 at 19:35 MSK](https://www.timeanddate.com/worldclock/fixedtime.html?day=24&month=6&year=2018&hour=19&min=35&sec=0&p1=166). There will be two versions of the contest, one for users in Division 1 and one for users in Division 2. Both versions will have six problems, with four problems shared between the versions.
The round will feature our friend and superstar member of ACM-ICPC team MIT TWO, Allen Liu ([user:cliu568,2019-06-19]).
The scoring distribution will be visible once the contest begins. As usual, we'd like to thank our wonderful problem coordinator [user:KAN,2018-06-19] and Codeforces administrator [user:MikeMirzayanov,2018-06-19], as well as the rest of the Codeforce...
The scoring distribution will be visible once the contest begins. As usual,
we'd like to thank our
Announcement of Codeforces Round 492 (Div. 1) [Thanks, uDebug!]
Announcement of Codeforces Round 492 (Div. 2) [Thanks, uDebug!]
167.
COMPFEST 13 Finals Mirror (Unrated, ICPC Rules, Teams Preferred) <img alt="logo" src="/predownloaded/31/e8/31e886f0ba055023282a2f68b4b254d98c02c727.png" style="float: right;height: 100.0px;margin: 10.0px;max-width: 100.0%;max-height: 100.0%;">
Hi <strong><span style="color:#bfac00;">Code</span><span style="color:#006fbf;">for</span><span style="color:#b00000;">ces</span></strong> ଘ(੭*ˊᵕˋ)੭* ੈ♡‧₊˚!
We're delighted to invite you to [COMPFEST 13 — Finals Online Mirror (Unrated, ICPC Rules, Teams Preferred)](https://codeforces.me/contests/1575) on <a class="contest-time" contestid=1575></a>.
All problems were written and prepared by [user:hocky,2021-09-18], [user:steven.novaryo,2021-09-18], [user:rama_pang,2021-09-18], [user:JulianFernando,2021-09-18], [user:Zap,2021-09-18], [user:Panji,2021-09-24], [user:richiesenlia,2021-09-24], [user:Sakamoto,2021-09-24], and [user:Markus_geger,2021-09-24].
I would also like to thank:
- [user:KAN,2021-09-18] for helping to host the mirror round;
- ([user:AVM.Martin,2021-09-30], [user:Ace_02,202...
IT event in Indonesia and competitive programming contest is one of the
competitions hosted.
168.
How I vibe coded a programming contests platform Hello old friends!
I recently decided to run an experiment: **could I build an entire programming challenges platform using nothing but an AI assistant**?
This post covers how that went, what I ended up with, and a few “you can’t make this up” moments along the way.
You can check it out [here](https://coding-platform-ochre.vercel.app/) (and solve problems in the ongoing contest) — feedback is welcome.
## Final architecture
* Next.js frontend + backend on Vercel
* Supabase Postgres for Users, Contests, Problems (including input/output files), and Submissions
* Private GitHub repo for problem development, plus a script to upsert them into the DB
* Redis cluster on Redis-Cloud for leaderboards and caching
## Development anecdotes
#### Day 1: instant success → instant disaster
July 28. I open Cursor IDE, set it to claude-4-sonnet, and say: “Make me a programming contest site with multiple ...
How I vibe coded a programming contests platform, IDE, set it to claude-4-sonnet, and say: “Make me a programming contest site
with multiple contests
169.
As an CNOI Gold Medalist: How I Train CNOI Gold Medal Winning Competitive Programmers This post is about:
1. The Main Two Abilities You Need in Competitive Programming
2. How to Choose Problems of an Appropriate Difficulty
3. How Should You Work on a Problem
4. When You Should Learn New Knowledge (Like New Algorithms)
5. How to Train Before an Important Contest
6. Free Content, Personalized Subscription Services, and Potential Opportunity for One-to-One Coaching
7. Survey About the Services
I won a gold medal at NOI 2024 in my second year of high school and was admitted to the Turing Class at Peking University. After securing my admission, I continued pursuing competitive programming: I began studying new material at university in advance while also challenging myself in higher-level competitions. During the winter of my final year of high school, I competed in the Universal Cup 2025 Finals and placed fifth among many strong contestants from around the world.
At the same time, I became a competitive programming coach because I wanted to give back to the ...
A programming contest contains several problems, and you need to write a program
for each of them
170.
[Tutorial] The command line: how to read input from file without #ifdef and much more #### Introduction
Instead of algorithms and math, I'll be doing something completely different here.
There is something that has bothered me for a long time: people not understanding
the tools they use to participate in contests and thus failing to take real advantage
of them. And it all goes back to not understanding the command line.
Some of you might say, "well surely, the command line is something obsolete and you're
only clinging to it because you [insert ridiculous amateur-psychology here]?"
No! The command line is not obsolete, and unless competitive programming becomes
so mainstream that software vendors start writing professional-grade tools aimed
specifically at us, it won't be.
[cut]
$~$
What is the command line? Any of these:
As you can see, it comes in many background colors and fonts, but the basic idea
is always the same. It's a box you can type commands in, which it will ...
programming that you have to do is test your program, at least on the sample
tests. The first thing that
171.
Divide by Zero 2021 and Codeforces Round #714 (Div. 2) [The Programming Club, IIT Indore](https://www.linkedin.com/company/progclub-iiti) is proud to present our flagship event, **Divide By Zero**! The contest will take place on [contest_time:1513]. This round will be rated for all participants with a rating lower than 2100.
Thanks to the following people for making the round possible:
- [user:KAN,2021-04-10] for coordinating throughout the round.
- [user:kalpitk,2021-04-10], [user:ajit,2021-04-10] and [user:7dan,2021-04-10] for setting the problems.
- [user:dvshah,2021-04-10], [user:bhanushali,2021-04-10], [user:sundesh,2021-04-10], [user:AniketSangwan,2021-04-10], [user:krishanu21saini,2021-04-10], [user:somyamehta_24,2021-04-10] and [user:hk2102,2021-04-10] for their contribution to the problemset.
- [user:Um_nik,2021-04-10], [user:dorijanlendvaj,2021-04-10], [user:chctxdy68,2021-04-10], [user:Osama_Alkhodairy,2021-04-10], [user:Scarle...
[The Programming Club, IIT
Indore](https://www.linkedin.com/company/progclub-iiti) is proud to
Announcement of Divide by Zero 2021 and Codeforces Round 714 (Div. 2)
172.
Codeforces: Calendar Hello, Codeforces!
The latest innovation in Codeforces is introduction Google calendar with information about the upcoming contests. To view calendar you can visit tab "Calendar" in the top menu.
The Codeforces contests are adding in calendar automatically. Also you can add contests from the other programming platforms. Each red user has this option. In addition, we will grant the rights to edit the calendar to employees/enthusiasts of other popular platforms.
In the tab "Add" you can add information about upcoming contest. The form shown below will help you for this.
Please, add to the calendar classic algorithmic contests which duration does not exceed a day. Also the contest must be publicly available, i. e. had English statements and open for a wide range of participants. We ask you to use short names for competitions, as it...
other programming platforms. Each red user has this option. In addition, we
will grant the rights to
173.
Bay Area Programming Contest 2026 The Bay Area Programming Contest ([link to last year's announcement](https://codeforces.me/blog/entry/139237)) returns on Sunday, March 1st, 2026. **This year, we will be hosting both a novice and advanced division.**
The estimated Codeforces ratings of the Novice problems range from 800 to 1900 (USACO Bronze to Gold). For Advanced, the estimated ratings range from 800 to 3000 (USACO Bronze to Platinum).
**If you are rated 1600+ or USACO Gold and above, you may only sign up for the Advanced Division.**
Detailed information, which will be updated as the contest day draws nearer, is at [bapc.gunncpc.com](bapc.gunncpc.com). You can register for the contest [at this link](https://docs.google.com/forms/d/e/1FAIpQLSdX04VD4NZjPy1-OmDPcXJQoe6nwF9XldqUMEqoHg3R2w_dUw/viewform).
All problems were created and prepared by [user:GusterGoose27,2026-02-12], [user:hihitherethere,2026-02-12], [user:Westin_sheep,2026-02-12], [user:Agent-Pea,2026-02-12], [user:Yttrialite,2026-02-12], and [use...
Bay Area Programming Contest 2026, **Contest format and rules:** Both the in-person contest and the online mirror
will be held, The Bay Area Programming Contest ([link to last year's
announcement](https://codeforces.me/blog
174.
Sumitomo Mitsui Trust Bank Programming Contest 2019 — Unofficial Editorial [Sumitomo Mitsui Trust Bank Programming Contest 2019](https://atcoder.jp/contests/sumitrust2019) has just finished, and this is an unofficial editorial.
Thanks to my friends [user:limruiy,2019-12-01] and [user:shenxy13,2019-12-01] for helping write some of the editorial.
[A — November 30](https://atcoder.jp/contests/sumitrust2019/tasks/sumitb2019_a)
==================
You can solve it simply by checking for each end date of the Gregorian calendar. However, note that as the second date directly follows the first date (a fact which I think is not clear in the English translation), we can also check whether they're in different months, or whether the second date is the first day of a month. This can be done in constant time.
[Code](https://atcoder.jp/contests/sumitrust2019/submissions/8724645)
[B — Tax Rate](https://atcoder.jp/contests/sumitrust2019/tasks/sumitb2019_b)
==================
We note that there is monotonicty in this question. $\lfloor 1.08(X+1) \rf...
Sumitomo Mitsui Trust Bank Programming Contest 2019 — Unofficial Editorial, [Sumitomo Mitsui Trust Bank Programming Contest
2019](https://atcoder.jp/contests/sumitrust2019
175.
The 3rd Universal Cup Announcement (with Details of Upcoming Online and Onsite Event on June 23!) <center>
<img src="/predownloaded/a6/3b/a63b8b0dc4b18f3e18c316abc22d4677aa075fd8.png" style="height: 262.0px;max-width: 100.0%;max-height: 100.0%;">
</center>
Hello everyone, we are happy to announce that the 3rd Universal Cup has started officially. Universal Cup is an organization dedicated to offering training resources for competitive programming teams. In the previous season, over 900 teams from more than 500 affiliations all over the world, registered and participated in a total of 28 stages, encompassing contests from Asia, Europe, and America. We also want to express our gratitude to our sponsor [Huawei](https://codeforces.me/blog/entry/122510).
- Semifinal and Summer Summit
---------------------------
As announced before ([Link](https://codeforces.me/blog/entry/127295)), we will host the 2nd Universal Cup Semifinal on June 23, 2024. The contest will start at 17:00 (UTC +8) and end at 22:00 (UTC +8).
**Any Universal Cup registered team can participate. If you are...
. Universal Cup is an organization dedicated to offering training resources for
competitiveprogramming teams
176.
Algoritmi Competitive Programming Academy Hello Codeforces Community,
I am _AmirReza PourAkhavan_,
- Over **8** years of teaching experience, including teaching at the Iran Team Selection Camp for **IOI**.
- Contest coordinator at LeetCode and formerly, **Codeforces**.
- ICPC World Finalist (twice) and took a high-honored place, **24**.
- Solved over **5000** problems on various platforms.
Along with my dedicated team, I am thrilled to introduce our new project focused on developing the next generation of competitive programmers. Having competed in and coached teams for the Iranian and International Olympiads in Informatics, we have experienced firsthand the significant impact of competitive programming. It is with great enthusiasm that we are launching an affordable, high-quality training program to prepare ambitious individuals for the challenges and opportunities of **IOI** and other competitive programming contests, like **ICPC**.
<center>
<br>
<img width="30%" src="/predownloaded/b6/f5/b6f5012e2a5f7ce09...
Algoritmi Competitive Programming Academy, competitive programming. It is with great enthusiasm that we are launching an
affordable, high-quality
177.
Polygon Updates (February 2022) Hello, Codeforces.
In this post, I'll share with you a few recent improvements in Polygon made by [user:MikeMirzayanov,2022-03-03], [user:unreal.eugene,2022-03-03], [user:dk318,2022-03-03] and me.
Polygon is a service to prepares programming problems and contests. It is usually used to prepare problems for olympiads/programming contests but it is also often used to prepare educational content. It is located at https://polygon.codeforces.com/ and is open to everybody.
Here are three recent new features:
* IOI-like Graders for Python
* Problem Materials
* User Groups
[cut]
<br/>
<br/>
IOI-like Graders for Python
==================
About 3 years ago we announced support of IOI graders for C++ in Polygon (Please read [the old post](https://codeforces.me/blog/entry/66916)). Now we have added support for graders written in Python. However, since there is no concept of linkage in Python, Python graders are different from C++ ones.
In the case of Python, the gra...
Polygon is a service to prepares programming problems and contests. It is
usually used to prepare
178.
Codeforces Round #850 Hello!
Welcome to [contest:1785] and [contest:1786] that will start on [contest_time:1785]. Both rounds will be rated.
This round is a mirror of VK Cup 2022 Final — annual programming championship for Russian-speaking competitors organized by VK. VK Cup [started in 2012](https://codeforces.me/vkcup2012) and has grown to be a five-track competition in competitive programming, Mobile, ML, Go, and JavaScript.
All the problems of Div. 1 round are authored and prepared by me, while [user:KAN,2023-02-05] authored and prepared two problems for Div. 2. Thanks to [user:errorgorn,2023-02-03], [user:irkstepanov,2023-02-03], [user:qwerty787788,2023-02-05], [user:Merkurev,2023-02-05], [user:IgorI,2023-02-05], [user:PavelKunyavskiy,2023-02-05], [user:izban,2023-02-05], [user:Alexdat2000,2023-02-05], [user:I_Remember_Olya_ashmelev,2023-02-05], [user:Akulyat,2023-02-05], [user:mike_live,2023-02-05], [user:Ekler,2023-02-05], [user:Kalashnikov,2023-02-05] for making this round better.
You w...
Hello! Welcome to [contest:1785] and [contest:1786] that will start on
[contest_time:1785]. Both
Announcement of VK Cup 2022 - Финальный раунд (Engine)
179.
On problem 2075B (ER176 B) and why it exists [SPOILERS] So, if you paricipated in ER 176 and got WA2 on problem B, you might think this is a terrible problem, maybe one of the worst on CF. Let me try to explain why it was created, and maybe it will change your opinion about it (or maybe it won't).
This problem has an obvious solution: you have to maximize the sum of the first $k$ chosen elements and the last element you paint, so the sum of $(k+1)$ elements of the array. So, let's take $(k+1)$ greatest elements, add them up, and we get the answer. It even passes the sample test case, but it is wrong.
<spoiler summary="Why it is wrong">
If $k=1$, there is only one "starting" element. So, the last element you paint must be on the border (the $1$-st or the $n$-th element of the array).
If $k>1$, the greedy solution actually works since any element between two elements which were initially chosen can be the last element. So, out of $(k+1)$ maximums, you can initially paint them all blue, except for the middle of them. But if $k=1$, yo...
solution or finding flaws in your ideas is a very important skill in
programming contests, and this
180.
CodeCraft-17 and Codeforces Round #391 (Div. 1 + Div. 2, combined) Announcement Hello Everyone!
I would like to invite you to CodeCraft-17, which will take place on [Thursday 12th January 2017, 9:05PM IST](https://www.timeanddate.com/worldclock/fixedtime.html?msg=CodeCraft-17&iso=20170112T1535&p1=1440&ah=3). The round will be a Div1 + Div2 combined round and is **rated**.
[Felicity, IIIT Hyderabad](https://www.facebook.com/felicity.iiith) presents [Threads ‘17](https://felicity.iiit.ac.in/threads/), the magnificent annual technical fest, is finally here in its 13th edition! With a plethora of intellectually engaging online contests in various fields of programming, mathematics and general knowledge, Threads is a celebration of the spirit of computing and engineering. The grand algorithmic sprint called **CodeCraft**, parallel programming in **Kernel Cruise**, mathematical enigmas in **Gordian Knot**, jeopardy style CTF event called **Break In**, overall Threads '17 has something to offer for every kind of computing enthusiast!
.
The [new C++ standard](http://en.wikipedia.org/wiki/C++11), also known as C++11 and also as C++0x is here, with some sugars for programming contest. I'll update this thread soon with new contents (and better structure).
You can use C++11 on Topcoder, Codeforces, HackerRank ...
This thread is based on my own experience, so you don't need to dig on the whole C++11 specification to find some useful feature you can use in programming contests.
### The "auto" keyword:
Type inference is included in many modern programming languages, and C++ is not behind, the "auto" keyword works like "var" in C#, it only tells the compiler to infer the type for us:
So,
~~~~~
map< string, pair< int, int > > somyLongTypeName = map< string, pair< int, int > >();
~~~~~
Can be shortened to, with no impact on speed, since the type is inferred at compile time:
~~~~~
auto longTypeNamesAreHistory = map< strin...
C++11 for programming contests..., is here, with some sugars for programming contest. I'll update this thread
soon with new contents
182.
Problem of cheating in Competitive Programming You are probably already familiar with the following cheating methods, submitting your solution on alt account, with 4o, and then deep seek, and then o1, and then o3, finding solutions on telegram, finding solutions on youtube, finding solutions on discord, asking your blue rated friend, asking your purple rated friend, asking your orange rated friend, asking your red rated friend, asking your lgm rated friend, play as a team of cyan, play as a team of blue, play as a team of purple, play as a team of orange, play as a team of red, play as a team of lgm, asking some other blue that is not your friend, asking some other purple that is not your friend, asking some other orange that is not your friend, asking some other red that is not your friend, asking some other Lgm that is not your friend, pay an orange to play the contest for you, pay a red to play the contest for you, pay an LGM to play the contest for you, print out katcl and bring it to IOI, print out cp-algorithm and bring it to...
Problem of cheating in Competitive Programming, friend, pay an orange to play the contest for you, pay a red to play the
contest for you, pay an LGM to
183.
Efficient and easy segment trees This is my first attempt at writing something useful, so your suggestions are welcome.
Most participants of programming contests are familiar with segment trees to some degree, especially having read this articles http://codeforces.me/blog/entry/15890, http://e-maxx.ru/algo/segment_tree (Russian only). If you're not — don't go there yet. I advise to read them after this article for the sake of examples, and to compare implementations and choose the one you like more (will be kinda obvious).
Segment tree with single element modifications
==================
Let's start with a brief explanation of segment trees. They are used when we have an array, perform some changes and queries on continuous segments. In the first example we'll consider 2 operations:
1. modify one element in the array;
2. find the sum of elements on some segment.
[cut]
.
### Perfect binary tree
I like to visualize a segment tree in the following way: [image link](http://i.imgur.com/GGBmcEP....
Most participants of programming contests are familiar with segment trees to
some degree
184.
OCPC 2025 Winter Singapore Mirror Camp (22-26 Feb) Hi everyone!
<center><img src="https://ocpc.camp/images/ocpc.svg" height="100px"></center>
For the [Winter 2025 edition of the Osijek Competitive Programming Camp (OCPC)](https://codeforces.me/blog/entry/138091), we are working with the [National University of Singapore (NUS)](https://www.nus.edu.sg/) to host a mirror of the OCPC in **Singapore**, during **22-26 Feb 2025**. The mirror will consist of 4 training contests, that are a subset of the main 7 contests of OCPC (scheduled for 15 Feb-23 Feb 2025 in Osijek, Croatia and online).
The contest days will be on 22, 23, 25 and 26 Feb, and 24 Feb will be a rest day. The mirror takes place right before [ICPC APAC Championship 2025](https://apac.icpc.global/), scheduled for 27 Feb-2 Mar, and is a good training opportunity for its participants. Please note that the mirror is a private initiative of NUS and OCPC, and is not an official part of the ICPC event.
If you want to get a feel of the contests, refer to [this comment](h...
For the [Winter 2025 edition of the Osijek Competitive Programming Camp
(OCPC)](https
185.
SIT STAR Contest <b><i>Hello!</i></b>
<b><i>Together with colleagues [Schaffhausen Institute of Technology](https://sit.org/) we hold such an event. If you want to study in Switzerland, then perhaps this is your chance!</i></b>
<b><i>— Mike</i></b>
Hello, Codeforces!
<center>
<img alt="SIT" src="https://static.tildacdn.com/tild6536-6661-4864-b937-393639346635/sit_logo_black_short.svg" style="float:right; height: 200px; margin: 10px; max-width:50%;"/>
</center>
We are thrilled to announce a new SIT STAR Contest by the [Schaffhausen Institute of Technology in Switzerland](https://sit.org/). The winners will have a chance to get a fully-funded Master’s scholarship in Computer Science and Software Engineering.
**<font color="red">What is the SIT STAR Contest?</font>**
The goal of the SIT STAR Contest is to promote interest in the field of Computer Science and Software Engineering, give students an opportunity to demonstrate their knowledge of programming, and be considered for...
SIT STAR Contest
186.
Codeforces LATOKEN Round 1 (Div. 1 + Div. 2) Editorial [problem:1534A]
Author: [user:Crackersamdjam,2021-06-13]
<spoiler summary="Hint 1">
Let's say you know the colour of the first square, what colours can you figure out next?
</spoiler>
<spoiler summary="Hint 2">
Colour it like a chessboard, but there's more than one possible chessboard!
</spoiler>
<spoiler summary="Hint 3">
Brute force the color of the first square!
</spoiler>
<spoiler summary="Tutorial">
[tutorial:1534A]
</spoiler>
<spoiler summary="Solution">
[submission:119400830]
</spoiler>
[problem:1534B]
Author: [user:Dormi,2021-06-13]
<spoiler summary="Hint 1">
Consider the contribution of each pillar to the answer.
</spoiler>
<spoiler summary="Hint 2">
How does doing the operation on a pillar change the contribution to the answer?
</spoiler>
<spoiler summary="Hint 3">
You only want to do an operation on a pillar if the top cell contributes 2 to the answer.
</spoiler>
<spoiler summary="Tutorial">
[tutorial:1534B]
</spoiler>
...
[Tests generator](https://github.com/zzaria/programming-contest
-resources/blob/main/my%20problems
Tutorial of Codeforces LATOKEN Round 1 (Div. 1 + Div. 2)
187.
EPIC Institute of Technology Round Summer 2025 (Codeforces Round 1036, Div. 1 + Div. 2) # Hello Codeforces Once Again
<img alt="" src="https://codeforces.me/predownloaded/4e/71/4e713a365fc86888c808b3b56d6fecfb529973e6.png" style="float:right; height: 154px; padding-left: 35px; padding-right: 73px; padding-top: 41px; padding-bottom: 33px;"/>
After months of hard work, [user:cry,2025-07-01], [user:Lilypad,2025-07-01] and I are extremely proud to welcome you to participate in [contest:2124] at [contest_time:2124]. This round is combined for Division 1 and Division 2, and it will be rated for everyone.
You will be given $3$ hours to solve $9$ problems. One problem will be split into two subtasks.
We would like to thank the following people for making the contest possible:
- [user:satyam343,2025-07-01] for outstanding coordination, working tirelessly with us to improve problem quality and donating his own problems to us. I cannot thank him enough.
- [user:Error_Yuan,2025-07-01] for proposing some ideas that weren't used in the end.
- [user:Benq,2025-07-01...
in [contest:2124] at [contest_time:2124]. This round is combined for Division
1 and Division 2, and
188.
TeamsCode Summer 2024 Virtual Programming Contest **UPD: The problems from the contest are available for upsolving at these links: [Novice Division Gym](https://codeforces.me/gym/105283) and [Advanced Division Gym](https://codeforces.me/gym/105284)**.
**UPD2: The editorial for the contest can be found at [this link](https://codeforces.me/blog/entry/132173)**.
Hello Codeforces! [TeamsCode](https://teamscode.org/) is excited to announce the [TeamsCode Summer 2024 Virtual Programming Contest](https://www.teamscode.org/contests/summer-2024/)! It will take place on [**Sunday, July 28 from 11:15 AM to 5:30 PM Pacific Time / 2:15 PM to 8:30 PM Eastern Time**](https://www.timeanddate.com/worldclock/fixedtime.html?msg=TeamsCode+Spring+2024+Virtual+Programming+Contest&iso=20240728T1115&p1=283&ah=6&am=15).
**Teams of up to 4 members will have 3 hours to solve around 10 problems.** The problem difficulties will range from Div 2. A to Div 1. F. There are two divisions: Novice and Advanced, so no matter what skill level you are, there i...
TeamsCode Summer 2024 Virtual Programming Contest, 2024 Virtual Programming Contest
](https://www.teamscode.org/contests/summer-2024/)! It will take
Announcement of TeamsCode Summer 2024 Novice Division
Announcement of TeamsCode Summer 2024 Advanced Division
189.
Invitation to CodeChef February Cook-Off 2023 (Rated for all) — 08th February We invite you to participate in CodeChef’s [February Cookoff 2023](https://www.codechef.com/COOK144?utm_source=discuss&utm_medium=organic&utm_campaign=COOK144), this Wednesday, 08th February, rated for all.
Time: [8 PM — 10:30 PM IST](https://www.timeanddate.com/worldclock/fixedtime.html?msg=CodeChef%20FebruaryCookoff%202023&iso=20230208T20&p1=44&ah=3)
<center>
</center>
<hr style="height:0.1px;border:none;color:#333;background-color:#333;" />
**From admins.** We apologize for the absence of Div. 1 contests. In the first half of 2022, we were trying hard to hold them on a regular basis. This was already challenging, as the number of high-quality proposals, especially hard ones, was very small; we had to use our own problems in almost every contest. This couldn't continue for long.
We would like Codechef Div. 1 contests to come back, but for this, we need your help. The Div....
), a Ukrainian programming camp that took place in the summer of 2022, and,
possibly, our own problems
190.
Interactive Problems: Guide for Participants Sometimes you can meet _interactive problems_ on programming contests (including Codeforces).
In problems of this type, the input data given to your program may be not predetermined but is built specifically for your solution. Jury writes a special program — _interactor_, such that its output is tranferred to the input of your solution, and the output of your program is sent to interactor’s input. In the other words, your solution and the interactor exchange the data and my decide what to print based on the "history of communication".
When you write the solution for the interactive problem it is important to keep in mind that if you output some data it is possible that this data is first placed to some internal buffer and may be not directly transferred to the interactor. In order to avoid such situation you have to use special `flush` operation _each time_ you output some data.
[cut]
There are these `flush` operations in standard libraries of almost all languages. Fo...
Sometimes you can meet _interactive problems_ on programming contests
(including Codeforces).
191.
Fixing the contest management mess ...or "How legacy systems fight obstacles no sane person would introduce in the first place".
Hello, Codeforces!
I am sure that those of you who tried to host their own programming competitions or write their own utilities for contest management are aware of the state of affairs regarding contest hosting. There are lots of incompatible formats, no one knows exactly how stuff ought to work, Polygon is full of nondescript and seemingly contradictory options, ej-polygon never seems to work quite correctly, modifications have to be applied to jury archives to make them work on your particular installation, non-trivial problem types require constant maintenance and hacks, *ad infinitum*.
Personally, I stumbled upon all these problems when I tried to get my own judge system working and suddenly discovered that the difficult part is not judging complex problems, but handling artificial complexity introduced by legacy software and standards. So here I am, attempting to solve these pro...
Fixing the contest management mess, I am sure that those of you who tried to host their own programming
competitions or write their own
192.
Stanford Local Programming Contest 2026 **Edit: Registration deadline extended by 12 hours -- to 9PM pacific time today!**
Hello Codeforces!
We ([user:ritwin,2026-03-26], [user:nikilrselvam,2026-03-26], [user:spycoderyt,2026-03-26], [user:lethan3,2026-03-26], [user:Mokuroh54,2026-03-26], [user:andy0liang,2026-03-26], [user:applepi216,2026-03-26], [user:bitset,2026-03-26], [user:minifinity,2026-03-26]) are excited to announce the
**Stanford Local Programming Contest (SLPC 2026)** — a 3-hour ICPC-style team contest with
**over $3,000 in prizes**!
SLPC has historically been Stanford's internal contest and ICPC team tryout. This year, we're
opening it up to the broader competitive programming community.
- **Date:** Saturday, April 4, 2026
- **Local Division:** In-person at Gates 403, Stanford students only -- lunch and boba provided!
- **Open Division:** Online, open to everyone
- **Registration deadline:** April 2, 2026 at 8:59 PM PDT
## Links
- [Website](https://cs.stanford.edu/group/acm/slpc/)
- [Regist...
Stanford Local Programming Contest 2026, SLPC has historically been Stanford's internal contest and ICPC team tryout.
This year, we're
193.
Codeforces Round #977 (Div. 2, based on COMPFEST 16 — Final Round) <img alt="logo" src="/predownloaded/7c/c9/7cc971d2212c2990000eca9584691770d4e6bc38.png" style="float: right;height: 100.0px;margin: 10.0px;max-width: 100.0%;max-height: 100.0%;">
Halo, **Codeforces**! Ape kabar kitak? Nyi deu sit bau maang? 😍 😍
COMPFEST 16 is happy to invite you to participate in [contest:2021] on [contest_time:2021]. The round will be **rated**. You will be given **2 hours** to solve **5 problems, 2 of them will have subtasks**.
**Note the unusual time of the round**.
------------------
The problems are written by [user:ArvinCiu,2024-10-05], [user:CyberSleeper,2024-10-05], [user:athin,2024-10-05], and [user:joelgun14,2024-10-05].
We would like to thank:
- [user:KAN,2024-10-05] for helping to host the round;
- [user:errorgorn,2024-10-05] for the based coordination;
- [user:gansixeneh,2024-10-05], [user:CyberSleeper,2024-10-05], [user:joelgun14,2024-10-05], and [user:icebear30,2024-10-05] for helping with the problem preparation;
...
IT event in Indonesia and competitive programming contest is one of the
competitions hosted.
194.
EZ Programming Contest #1 Announcement ### Hello, Codeforces!
I would like to invite you all to my first contest, [contest:103150]. It will be held on [contest_time:103150]. The round is not rated for anybody, since it is an unofficial contest.
The contest has $n$ problems, where $n$ is an integer satisfying $7 \leq n \leq 11$. You will have 2 hours and 30 minutes to solve the problems. The problems are meant to be **about Div. 2 A, B, and C level**, and they will _not_ be sorted in order of difficulty. So, you can think of the problemset like if ICPC only went up to Div. 2 C.
A huge thanks to my testers [user:wabadabakalakaboo,2021-06-19], [user:manish.17,2021-06-19], and [user:fishy15,2021-06-19]!
I know you all are filled with questions, so I'll try to answer them all now.
- Q: _Is it rated?_
- A: No.
- Q: _Why did you write this contest?_
- A: I have a lot of ideas for easy Div. 2 A, B, and C level problems, not all of which can get into a contest. I thought it would be fun to compile them all into...
EZ Programming Contest #1 Announcement, competitive programming :P.
Announcement of EZ Programming Contest #1
195.
Competitive Programming in the Era of AI **Read the original post on :** https://www.vibhaas.net/posts/Competitive-Programming-in-the-era-of-AI/
<br>
<div align="center">
<img src="/predownloaded/3e/ae/3eaee0e93cf1784ab4923157729c81dd3a080fcf.jpg"
alt="Wanderer above the Sea of Fog, Caspar David Friedrich"
width="70%">
<br>
<small><i>Wanderer above the Sea of Fog, Caspar David Friedrich</i></small>
</div>
<blockquote>
Picture this. You've had a draining week at university or at work. You're exhausted, and you need a break. Most people would play a few video games, grab a few beers with their friends, or just sleep. But you have the (mis?)-fortune of being addicted to this weird, aesthetically questionable website called Codeforces (or AtCoder, or whatever your favorite OJ is).
</blockquote>
<blockquote>
You check the list of upcoming contests, and you're in luck. "Nice," you think to yourself, "two rated contests back to back!" This is going to allow you to farm some rating! ...
Competitive Programming in the Era of AI, After a long time away from competitive programming, one day, you decide to
give contests again
196.
Report: Contest-Time Solution Hints Linked to NotOnlySuccess I am writing this blog to report a competitive-integrity issue involving the Codeforces user [user:NotOnlySuccess,2026-08-09] and a website associated with their content.
The main issue is simple: **problem-specific solution material and hints for an ongoing Codeforces contest were made available before the contest ended.**
# 1. Solution material published before the contest ended
During [Codeforces Round 1116 (Div. 1, Div. 2)](https://codeforces.me/blog/entry/155668), an article titled [CF Round 1116 (Div. 1+2)](https://mp.weixin.qq.com/s/P3QJqmQFRsLlW9GX_y_8YQ) was published on a WeChat public account at August 10, 2026, 00:37 (UTC +8). The Codeforces contest ended at August 10, 2026, 01:05 (UTC +8).
Therefore, the article was publicly available **28 minutes before the contest ended**.
The article already contained problem-specific solution material.
For readers who do not understand Chinese...
Report: Contest-Time Solution Hints Linked to NotOnlySuccess, There are also earlier examples of solution material being published before
otherprogramming
197.
The 1st Universal Cup. Stage 13: Iberia Hello Codeforces! The 13th Stage of the 1st Universal Cup is coming. It will be held from April 22nd to 23rd.
This contest was first used in the Petrozavodsk Programming Camp Winter 2023, and also appeared in the 2023 ICPC Training Camp powered by Huawei and the Hello Muscat 2023 Bootcamp. If you participated in any of those, you should not participate in this stage of the Universal Cup.
All the problems were authored and prepared by [user:998batrr,2023-04-21], [user:244mhq,2023-04-21], [user:353cerega,2023-04-21] (Harbour.Space [P+P+P](https://codeforces.me/team/102621), Barcelona, Spain) and [user:Um_nik,2023-04-21] (Lisbon, Portugal).
We want to thank the Universal Cup Committee for staying true to the spirit of 5h/3person/1pc contests and for providing the opportunity to share our contest with a wider audience.
As usual, we have three time windows for participating. You can participate in the contest in the following three time windows:
[Time Window 1: April 22nd 13...
This contest was first used in the Petrozavodsk Programming Camp Winter 2023,
and also appeared in
198.
OCPC 2026 Summer Hi everyone!
<center><a href="https://ocpc.camp"><img src="https://ocpc.camp/images/ocpc_light.svg?nocache" height="80px"></a>
<a href="https://icpc.foundation/"><img src="https://ocpc.camp/images/ICPC.svg?nocache" height="80px"></a></center>
The [OCPC](https://ocpc.camp/) (Osijek Competitive Programming Camp), an [award-winning](https://www.linkedin.com/feed/update/urn:li:activity:7368330111089131522/) camp for university students preparing for ICPC and other coding competitions, is back this **Summer 2026** — this time with **two onsite editions**:
- **Hong Kong** — **8–16 August 2026**, hosted at the City University of Hong Kong.
- **Iași, Romania** — **12–20 September 2026**, hosted at Alexandru Ioan Cuza University of Iași.
Both editions are organized by us together with local hosts at each site, and use the **same contest set** — so you take part in **one** of them. As a rough guide, the **Iași** edition is most convenient for teams based in Europe, and **Hong Kong*...
contest set** — so you take part in **one** of them. As a rough guide, the
**Iași** edition is most
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